Polypropylene composition

Abstract

The present invention relates to a polypropylene composition comprising: a) a bimodal random Ziegler-Natta propylene copolymer having a comonomer content of 2.0 to 4.5 wt.-%, the copolymer comprising: (i) 30 to 70 wt.-% of a first propylene copolymer, the comonomer content being in the range of 0.1 to 4.5 wt.-%, relative to the total weight of the first propylene copolymer, and an MFR2 of 1 to 100 g / 10 min; and (ii) 70 to 30 wt.-% of a second propylene copolymer, the comonomer content being in the range of 1.0 to 15 wt.-%, relative to the total weight of the second propylene copolymer, and an MFR2 of 1 to 100 g / 10 min; with the proviso that the comonomer content of the second propylene copolymer (ii) is higher than the comonomer content of the first propylene copolymer (i); and b) at least one hindered amine light stabilizer.

Description

Technical Field

[0001] The present invention relates to a polypropylene composition. More specifically, the present invention relates to a polypropylene composition comprising a bimodal random Ziegler-Natta propylene copolymer and at least one hindered amine light stabilizer. The present invention also relates to a method for preparing the polypropylene composition and an article comprising the polypropylene composition. Background Art

[0002] Polypropylene (PP) is one of the most commonly used plastics in packaging applications. In this growing market, especially in the pharmaceutical sector, as well as in food packaging, and especially in medical applications (syringes, bags, tubes, etc.), the material is sterilized by heat (steam), radiation (beta / electron or gamma) or chemicals (mainly ethylene oxide), which affects the mechanical and optical properties.

[0003] Of all these methods, gamma irradiation sterilization is the most suitable for sterilizing pharmaceuticals, medical, or diagnostic items. It is well known that irradiation, primarily the action of gamma rays, causes chain scission and degradation, leading to a decrease in melt viscosity and severe embrittlement. This free radical reaction is so important because it persists long after the actual sterilization process, necessitating long-term studies to understand its effects. Various strategies have been described to mitigate these effects. Some focus on the use of "flow agents" (paraffin oil) and specialized stabilizer formulations. Others combine polypropylene with specific polyethylene properties or other polymers, as described in EP0847420, JP4808419, and KR2005053937.

[0004] In "Effects of Sterilization on Polypropylene," presented at the 9th European PLACE Conference in Rome (2003), Markus Gahleitner et al. described changes in the mechanical properties of various polypropylene homopolymers and random copolymers after irradiation to 50 kGy. These results describe mechanical properties in the short term after sterilization. However, these results do not describe the long-term properties of irradiated polymer samples.

[0005] In the healthcare industry, there is a continuing need for polymers for use in medical articles that can withstand higher doses of radiation and maintain high levels and longer durations of mechanical properties, such as impact resistance, after exposure to radiation.

[0006] WO 2018 / 210893 describes a unimodal random propylene copolymer with improved gamma sterilization performance. WO 2019 / 197383 discloses a composition comprising a bimodal polypropylene random copolymer prepared using a metallocene catalyst together with a soluble nucleating agent, which is found to have improved resistance to gamma radiation.

[0007] The present inventors have sought new polypropylene compositions, particularly for the healthcare and medical markets, with improved resistance to gamma radiation. This improvement should not be at the expense of any other properties of the polymer or any article formed therefrom. Thus, other mechanical properties, such as hardness or a low content of components soluble in cold xylene (XCS), should be maintained.

[0008] The present inventors have surprisingly discovered that polypropylene compositions comprising bimodal random Ziegler-Natta copolymers and at least one hindered amine light stabilizer provide an attractive solution. In particular, these polypropylene compositions exhibit attractive toughness after sterilization. Notably, this toughness is maintained over an extended period, indicating good gamma sterilization stability. Summary of the Invention

[0009] Thus, viewed from a first aspect, the present invention provides a polypropylene composition comprising:

[0010] a) a bimodal random Ziegler-Natta propylene copolymer having a comonomer content of 2.0 to 4.5 wt%, said copolymer comprising:

[0011] (i) 30 to 70 wt% of a first propylene copolymer having a comonomer content in the range of 0.1 to 4.5 wt%, relative to the total weight of the first propylene copolymer, and an MFR2 of 1 to 100 g / 10 min; and

[0012] (ii) 70 to 30 wt% of a second propylene copolymer having a comonomer content in the range of 1.0 to 15 wt%, relative to the total weight of the second propylene copolymer, and an MFR2 of 1 to 100 g / 10 min;

[0013] with the proviso that the comonomer content of the second propylene copolymer (ii) is higher than the comonomer content of the first propylene copolymer (i); and

[0014] b) at least one hindered amine light stabilizer.

[0015] Viewed from another aspect, the invention provides a process for the preparation of a polypropylene composition as hereinbefore defined, said process comprising the steps of:

[0016] a) in a first reactor, preferably a slurry reactor, polymerizing a mixture comprising propylene and one or more selected from ethylene and C4-C 10 a-olefin to obtain a first propylene polymer component having a comonomer content in the range of 0.1 to 4.5 wt%,

[0017] b) in a second reactor, preferably a gas phase reactor, polymerizing a propylene polymer component comprising propylene and one or more selected from ethylene and C4-C 10 a monomer containing a comonomer of an alpha olefin to obtain a second propylene polymer component having a comonomer content in the range of 1.0 to 15 wt%,

[0018] c) extruding the polymer component in the presence of at least one hindered amine light stabilizer;

[0019] The polymerization is carried out in the presence of a Ziegler-Natta catalyst.

[0020] Viewed from another aspect the invention provides an article comprising the polypropylene composition as hereinbefore defined.

[0021] definition

[0022] The term "polypropylene" is to be understood as a propylene-based polymer, ie a polymer comprising at least 50 wt% propylene, based on the total weight of the polymer as a whole. The terms "polypropylene" and "propylene polymer" have the same meaning and are used interchangeably.

[0023] In the context of the present invention, the term "gamma sterilizable" means that the polymer is capable of being sterilized by the use of gamma radiation. Those skilled in the art will be familiar with gamma sterilization techniques. Gamma sterilization is typically performed in a dose range of 15 to 150 kGy.

[0024] The term "random copolymer" must preferably be understood according to IUPAC (Pure Appl. Chem., Vol. No. 68, 8, pp. 1591 to 1595, 1996).

[0025] Detailed description

[0026] The present invention relates to a polypropylene composition comprising a bimodal random propylene copolymer and at least one hindered amine light stabilizer.

[0027] Bimodal random propylene copolymer

[0028] The bimodal random Ziegler-Natta propylene copolymer used in the composition of the present invention comprises:

[0029] (i) 30 to 70 wt% of a first propylene copolymer having a comonomer content in the range of 0.1 to 4.5 wt%, relative to the total weight of the first propylene copolymer, and an MFR2 of 1 to 100 g / 10 min; and

[0030] (ii) 70 to 30 wt% of a second propylene copolymer having a comonomer content in the range of 1.0 to 15 wt%, relative to the total weight of the second propylene copolymer, and an MFR2 of 1 to 100 g / 10 min;

[0031] With the proviso that the comonomer content of the second propylene copolymer (ii) is higher than the comonomer content of the first propylene copolymer (i).

[0032] While it is within the scope of the present invention that the bimodal random propylene copolymer comprises other polymer components, it is preferred that the first and second propylene copolymers (i) and (ii) are the only polymer components, i.e. the bimodal random propylene copolymer consists of the above components (i) and (ii).

[0033] Bimodal random Ziegler-Natta propylene copolymers are propylene copolymers comprising propylene and one or more comonomers. Preferably, the one or more comonomers are selected from ethylene and C4-C10 α-olefins, preferably from ethylene and C4-C8 α-olefins, more preferably from ethylene and C4-C6 α-olefins, even more preferably one or more comonomers comprising ethylene, and even more preferably the comonomers are selected only from ethylene.

[0034] Thus, in a preferred embodiment the propylene-random copolymer comprises, preferably consists of, propylene and ethylene as monomer units.

[0035] The bimodal random Ziegler-Natta propylene copolymer has a total comonomer content of 2.0 to 4.5 wt%, preferably 3.0 to 4.2 wt%, relative to the total weight of the copolymer.

[0036] The bimodal random Ziegler-Natta propylene copolymer may have a melt flow rate (MFR2) of 1.0 to 60 g / 10 min, preferably 5.0 to 45 g / 10 min, more preferably 15 to 30 g / 10 min. MFR2 is determined according to ISO 1133 at a temperature of 230°C and a load of 2.16 kg.

[0037] The random propylene copolymer is bimodal with respect to molecular weight distribution and / or comonomer content.

[0038] First propylene copolymer (i)

[0039] The first propylene copolymer (i) is present in an amount of 30 to 70 wt%, preferably 35 to 65 wt%, more preferably 45 to 55 wt%, relative to the total weight of the bimodal propylene copolymer.

[0040] The first propylene copolymer (i) is a propylene copolymer comprising propylene and one or more comonomers. Preferably, the one or more comonomers are selected from ethylene and C4-C10 α-olefins, preferably ethylene and C4-C8 α-olefins, more preferably ethylene and C4-C6 α-olefins, even more preferably one or more comonomers comprising ethylene, and even more preferably the comonomers are selected only from ethylene.

[0041] Therefore, in a preferred embodiment, the first propylene copolymer comprises, preferably consists of, propylene and ethylene as monomer units.

[0042] The total comonomer content of the first propylene copolymer (i) is in the range of 0.1 to 4.5 wt.-%, preferably in the range of 0.4 to 2.5 wt.-%, more preferably in the range of 0.6 to 1.5 wt.-%, relative to the total weight of the first propylene copolymer (i). The comonomer content of the first propylene copolymer (i) is lower than the comonomer content of the second propylene copolymer (ii). Therefore, the first propylene copolymer (i) can be regarded as a comonomer-poor component, while the second propylene copolymer (ii) can be regarded as a comonomer-rich component.

[0043] The melt flow rate (MFR2) of the first propylene copolymer (i) may be in the range of 1.0 to 100 g / 10 min, preferably in the range of 15 to 40 g / 10 min, more preferably in the range of 17 to 35 g / 10 min. MFR2 is determined according to ISO 1133 at a temperature of 230°C and a load of 2.16 kg.

[0044] Second propylene copolymer (ii)

[0045] The second propylene copolymer (ii) is present in an amount of 70 to 30 wt%, preferably 65 to 35 wt%, more preferably 55 to 45 wt%, relative to the total weight of the bimodal propylene copolymer.

[0046] The second propylene copolymer (ii) is a propylene copolymer comprising propylene and one or more comonomers. Preferably, the one or more comonomers are selected from ethylene and C4-C10 α-olefins, preferably from ethylene and C4-C8 α-olefins, more preferably from ethylene and C4-C6 α-olefins, even more preferably one or more comonomers comprising ethylene, and even more preferably the comonomers are selected only from ethylene.

[0047] Accordingly, in a preferred embodiment the second propylene copolymer comprises, preferably consists of, propylene and ethylene as monomer units.

[0048] The total comonomer content of the second propylene copolymer (ii) is in the range of 1.0 to 15 wt.-%, preferably in the range of 3.0 to 10 wt.-%, more preferably in the range of 5.0 to 8.0 wt.-%, relative to the total weight of the second propylene copolymer (ii). The comonomer content of the first propylene copolymer (i) is lower than the comonomer content of the second propylene copolymer (ii). Therefore, the first propylene copolymer (i) can be regarded as a comonomer-poor component, while the second propylene copolymer (ii) can be regarded as a comonomer-rich component.

[0049] The melt flow rate (MFR2) of the second propylene copolymer (ii) may be in the range of 1.0 to 100 g / 10 min, preferably in the range of 15 to 40 g / 10 min, more preferably in the range of 17 to 35 g / 10 min. MFR2 is determined according to ISO 1133 at a temperature of 230°C and a load of 2.16 kg.

[0050] Preparation of bimodal random propylene copolymers

[0051] The bimodal random Ziegler-Natta propylene copolymer used in the polypropylene composition of the present invention can be produced by any known polymerization process and polymerization technique.

[0052] Preferably, the bimodal random Ziegler-Natta propylene copolymer used in the polypropylene composition of the present invention is typically produced in a sequential polymerization process. The term "sequential polymerization process" as used herein means producing the propylene polymer component in a process comprising at least two reactors connected in series. In a preferred embodiment, the term "sequential polymerization process" as used herein means conveying the reaction mixture of the first reactor, i.e. the first propylene copolymer (i) and unreacted monomers, preferably directly, into the second reactor, where the second propylene copolymer (ii) is obtained.

[0053] Thus, the bimodal propylene copolymer is preferably produced by a process comprising at least a first reactor and a second reactor. The process may comprise at least one additional polymerization reactor after the second reactor. In a specific embodiment, the process consists of two polymerization reactors, i.e. a first reactor and a second reactor. The term "polymerization reactor" shall indicate that the polymerization reaction mainly takes place. Thus, in case the process consists of two or more polymerization reactors, this definition does not exclude the option that the overall process comprises a prepolymerization step, e.g. in a prepolymerization reactor. The term "consisting of" is a closed expression only for the main polymerization reactor. In case the overall process according to the present invention comprises a prepolymerization reactor, the term "first propylene copolymer component" refers to the (co)polymer produced in the prepolymerization reactor.

[0054] The sum of polymer and (co)polymer produced in the first reactor.

[0055] The reactor is typically selected from a slurry reactor and a gas phase reactor.

[0056] The first reactor is preferably a slurry reactor and can be any continuous or simple stirred batch tank reactor or loop reactor performing bulk polymerization or slurry polymerization. The "bulk polymerization" refers to the process of polymerization in liquid monomer, essentially in the absence of inert diluents. However, it is known to those skilled in the art that monomers used in commercial production are never pure but always contain aliphatic hydrocarbons as impurities. For example, propylene monomer may contain up to 5% of propane as an impurity. Therefore, the "bulk polymerization" preferably refers to polymerization in a reaction medium comprising at least 60% (weight / weight) monomer. According to the present invention, the first reactor is more preferably a loop reactor.

[0057] The second reactor is preferably a gas phase reactor. The gas phase reactor can be any mechanically mixed or fluidized bed reactor or a settled bed reactor. Preferably, the gas phase reactor comprises a mechanically stirred fluidized bed reactor having a gas velocity of at least 0.2 m / s. The gas phase reactor of the fluidized bed type reactor may further comprise a mechanical stirrer to promote mixing within the fluidized bed.

[0058] The possible subsequent polymerization reactor or reactors are preferably gas phase reactors.

[0059] A preferred polymerization process is a "loop gas phase" process, such as that developed by Borealis and known as the BORSTART™ technology. Examples of such polymerization processes are described in EP0887379, WO92 / 12182, WO2004 / 000899, WO2004 / 111095, WO99 / 24478, WO99 / 24479 and WO00 / 68315.

[0060] When the overall process according to the present invention includes a prepolymerization reactor, the prepolymerization step occurs before the polymerization in the first reactor. The prepolymerization step occurs in the prepolymerization reactor, wherein propylene is pre-(co)polymerized. According to the present invention, the prepolymerization reactor has smaller dimensions than the first reactor, the second reactor, and the subsequent polymerization reactor(s), respectively. The reaction volume of the prepolymerization reactor can be, for example, 0.001% to 10% of the reaction volume of the first reactor, such as a loop reactor. In the prepolymerization reactor, propylene is pre-(co)polymerized in bulk or slurry to produce propylene (co)polymer.

[0061] The operating temperature in the prepolymerization reactor is generally in the range of 0 to 60°C, preferably in the range of 15 to 50°C, more preferably in the range of 18 to 35°C.

[0062] The pressure in the prepolymerization reactor is not critical, but must be high enough to keep the reaction mixture in the liquid phase. Thus, the pressure in the prepolymerization reactor may be in the range of 20 to 100 bar, preferably in the range of 30 to 70 bar.

[0063] Hydrogen may be added in the prepolymerisation reactor to control the molecular weight and thus the melt flow rate MFR2 of the propylene (co)polymer produced in the prepolymerisation reactor.

[0064] In the first reactor of the process of the present invention, a monomer feed comprising propylene and one or more comonomers is added, wherein the comonomers are preferably selected from ethylene and C4-C 10 α-olefin. In the case of a prepolymerization step in the process, the propylene (co)polymer produced in the prepolymerization reactor is also added to the first reactor. In the first reactor, the first propylene polymer component is obtained. It should be understood that the "first propylene polymer component" is equivalent to the first propylene copolymer (i) of the present invention.

[0065] Relative to the total weight of the first propylene polymer component, the comonomer content of the first propylene polymer component is preferably selected from ethylene and C4-C 10 % by weight, preferably in the range of 0.4 to 2.5 wt%, and more preferably in the range of 0.6 to 1.0 wt%.

[0066] Generally speaking, the melt flow rate (MFR2) of the first propylene polymer component may be in the range of 1.0 to 100 g / 10 min, preferably in the range of 15 to 40 g / 10 min, more preferably in the range of 17 to 35 g / 10 min. MFR2 is measured according to ISO 1133 at a temperature of 230°C and a load of 2.16 kg.

[0067] The operating temperature in the first reactor is typically in the range of 62 to 85°C, preferably in the range of 65 to 82°C, more preferably in the range of 67 to 80°C.

[0068] Typically, the pressure in the first reactor is in the range of 20 to 80 bar, preferably in the range of 30 to 70 bar, more preferably in the range of 35 to 65 bar.

[0069] Hydrogen may be added in the first reactor to control the molecular weight and thus the melt flow rate MFR2 of the first propylene polymer component produced in the first reactor.

[0070] Typically, the hydrogen / propylene (H2 / C3) ratio in the first reactor is in the range of 1.5 to 6.0 mol / kmol, preferably in the range of 1.6 to 5.5 mol / kmol, more preferably in the range of 1.7 to 5.0 mol / kmol.

[0071] Typically, the one or more comonomers (preferably selected from ethylene and C4-C 10 The ratio of C1-α-olefins to C3 is lower than 10.0 mol / kmol, preferably in the range of 0.0 to 8.0 mol / kmol, more preferably in the range of 0.0 to 7.5 mol / kmol.

[0072] Typically, the reaction mixture of the first reactor is fed into the second reactor, preferably directly. The term "direct feeding" refers to a process in which the reaction mixture of the first reactor is directly introduced into the next polymerization step, i.e., into the second reactor. 10 α-olefin, is added into the second reactor. In the second reactor, the second propylene polymer component is obtained. It should be understood that the "second propylene polymer component" is equivalent to the "second propylene copolymer (ii)" of the present invention. The second propylene polymer component is produced in the presence of the first propylene polymer component, thereby generating the bimodal random copolymer of the present invention in situ.

[0073] Those skilled in the art will appreciate that the material leaving said second reactor comprises first and second propylene polymer components two parts.This mixture is a bimodal random copolymer of the present invention.Therefore, directly any measurement that the material leaving said second reactor is carried out will reflect the character of bimodal random copolymer of the present invention, rather than the character of the second propylene polymer component.According to these measurements, together with the measurement of the material leaving said first reactor (being the first propylene polymer component), can calculate the character of the second propylene polymer component based on known method.

[0074] Relative to the total weight of the second propylene polymer component, the content of the comonomer of the second propylene polymer component is preferably selected from ethylene and C4-C 10 α-olefins, in the range of 1.0 to 15 wt%, preferably in the range of 3.0 to 10 wt%, more preferably in the range of 5.0 to 8.0 wt%.

[0075] Typically, the melt flow rate (MFR2) of the second propylene polymer component may be in the range of 1 to 100 g / 10 min, preferably in the range of 15 to 40 g / 10 min, more preferably in the range of 17 to 35 g / 10 min. MFR2 is measured according to ISO 1133 at a temperature of 230°C and a load of 2.16 kg.

[0076] The operating temperature in the second reactor is generally in the range of 70 to 95°C, preferably in the range of 75 to 90°C, more preferably in the range of 78 to 88°C.

[0077] Typically, the pressure in the second reactor is in the range of 5 to 50 bar, preferably in the range of 15 to 40 bar.

[0078] Hydrogen may be added in the second reactor to control the molecular weight and thus the melt flow rate MFR2 of the second propylene polymer component produced in the second reactor.

[0079] Typically, the hydrogen / propylene (H2 / C3) ratio in the second reactor is in the range of 12.0 to 70.0 mol / kmol, preferably in the range of 15.0 to 60.0 mol / kmol, more preferably in the range of 16.0 to 50.0 mol / kmol.

[0080] Typically, one or more comonomers (preferably selected from ethylene and C4-C 10 The ratio of C1-α-olefins to C3 is in the range of 4.5 to 20.0 mol / kmol, preferably in the range of 5.0 to 18.0 mol / kmol, more preferably in the range of 5.5 to 17.0 mol / kmol.

[0081] In the process according to the present invention the propylene polymer produced in the first reactor, i.e. the first propylene copolymer (i), is typically produced in an amount in the range of 30 to 70 wt.-%, preferably in the range of 40 to 60 wt.-%, more preferably in the range of 45 to 55 wt.-%, based on the total weight of the bimodal propylene copolymer.

[0082] In the process according to the present invention the propylene polymer produced in the second reactor, i.e. the second propylene copolymer (ii), is typically produced in an amount in the range of 30 to 70 wt.-%, preferably in the range of 40 to 60 wt.-%, more preferably in the range of 45 to 55 wt.-%, based on the total weight of the bimodal propylene copolymer.

[0083] The comonomer content of the second propylene copolymer (ii) is higher than the comonomer content of the first propylene copolymer (i).

[0084] Preferably selected from ethylene and C4-C 10 One or more comonomers of α-olefins are incorporated in different amounts into the reactor of the process of the present invention to produce propylene copolymers having a bimodal copolymer distribution with respect to the copolymer content of each propylene polymer contained therein, i.e. the first propylene copolymer (i) and the second propylene copolymer (ii).

[0085] In the process according to the invention, the one or more comonomers are preferably selected from ethylene and C4-C 10 α-olefins, more preferably selected from ethylene and C4-C8 α-olefins, even more preferably selected from ethylene and C4-C6 α-olefins, even more preferably selected from one or more comonomers comprising ethylene, further more preferably the comonomer is selected only from ethylene.

[0086] After polymerization in the second reactor step the first and second propylene polymer fractions (which together are the bimodal random copolymer of the present invention) are recovered by conventional methods known to those skilled in the art.

[0087] The recovered bimodal random copolymer is generally in the form of particles.

[0088] Typically, the bimodal random copolymer recovered from the polymerization process is extruded in the presence of at least one hindered amine light stabilizer and any other optional components to produce the polypropylene composition of the present invention.

[0089] The extruder for performing the extrusion step can be any extruder known in the art. The extruder can be a single screw extruder, a twin screw extruder, such as a co-rotating twin screw extruder or a counter-rotating twin screw extruder, or a multi-screw extruder, such as a ring extruder. Preferably, the extruder is a single screw extruder or a twin screw extruder. Particularly preferably, the extruder is a co-rotating twin screw extruder.

[0090] The extruder generally comprises a feed zone, a melting zone, a mixing zone, and optionally a die zone.

[0091] The length to diameter ratio L / D of the extruder does not exceed 60:1, preferably does not exceed 40:1.

[0092] The extruder may also have one or more feed ports for adding other components, such as additives, to the extruder. The location of such additional feed ports depends on the type of material being added through the port.

[0093] A polymerization catalyst is also present in the method of the present invention. The polymerization catalyst is a Ziegler-Natta catalyst. Propylene polymerized in the presence of the Ziegler-Natta catalyst is referred to as "Ziegler-Natta propylene." Typically, the polymerization Ziegler-Natta catalyst comprises one or more Group 4 to Group 6 transition metal (TM) compounds, such as titanium, as defined in the 2013 edition of IUPAC, and further comprises a Group 2 metal compound, such as a magnesium compound, and an internal electron donor (ID).

[0094] The components of the catalyst may be supported on a particulate support, such as an inorganic oxide, such as silicon dioxide or aluminum oxide. Alternatively, the magnesium halide may form a solid support. The catalyst components may also be prepared by emulsion solidification or precipitation methods, as is well known to those skilled in the art of catalyst preparation, rather than being supported on an external support.

[0095] Preferably, a specific type of Ziegler-Natta catalyst is present in the method of the present invention. In this specific type of Ziegler-Natta catalyst, the internal electron donor must be a non-phthalic acid compound. Preferably, no phthalate compounds are used throughout the preparation process of the specific type of Ziegler-Natta catalyst, so that the specific type of Ziegler-Natta catalyst ultimately does not contain any phthalic acid compounds. Therefore, the specific type of Ziegler-Natta catalyst does not contain phthalic acid compounds. Therefore, the bimodal random copolymer of the present invention does not contain phthalic acid compounds.

[0096] Typically, the specific type of Ziegler-Natta catalyst comprises an internal electron donor (ID) which is selected as a non-phthalic acid compound, in such a way that the specific type of Ziegler-Natta catalyst is completely free of phthalic acid compounds. Furthermore, the specific type of Ziegler-Natta catalyst can be a solid catalyst, preferably free of any external support material, such as silica or MgCl2, so that the solid catalyst is self-supported.

[0097] Solid catalysts can usually be obtained by the following conventional methods:

[0098] a) providing a solution:

[0099] a1) at least one Group 2 metal alkoxide (Ax) which is the reaction product of a Group 2 metal compound with an alcohol (A) which, in addition to the hydroxyl moiety, comprises at least one ether group, optionally in an organic liquid reaction medium; or

[0100] a2) at least one Group 2 metal alkoxide (Ax') which is the reaction product of a Group 2 metal compound with an alcohol mixture of an alcohol (A) and a monohydric alcohol (B) of the general formula ROH, optionally in an organic liquid reaction medium; or

[0101] a3) A mixture of a Group 2 metal alkoxide (Ax) and a Group 2 metal alkoxide (Bx), which is a reaction product of a Group 2 metal compound and a monohydric alcohol (B), optionally in an organic liquid reaction medium; or

[0102] a4) A Group 2 metal alkoxide of the formula M(OR1) n (OR2) m X 2-n-m or a Group 2 alkoxide M(OR1) n' X 2-n' and M(OR2) m' X 2-m' where M is a Group 2 metal, X is a halogen, R1 and R2 are different alkyl groups having 2 to 16 carbon atoms, and 0 ≤ n ≤ 2, 0 ≤ m < 2 and n + m + (2 - n - m) = 2, provided that n and m are not both 0, 0 < n' ≤ 2 and 0 < m' ≤ 2; and

[0103] b) Adding the solution of step a) to a compound of at least one transition metal from Group 4 to Group 6, and

[0104] c) Obtaining solid catalyst component particles,

[0105] and adding a non-phthalic internal electron donor (ID) at least in one step before step c).

[0106] Preferably, the internal electron donor (ID) or its precursor is added to the solution of step a), or added to the transition metal compound before adding the solution of step a).

[0107] According to the above process, the solid catalyst can be obtained by a precipitation method or an emulsion curing method, depending on the physical conditions, especially the temperature used in steps b) and c). An emulsion is also called a liquid-liquid two-phase system. In both methods (precipitation method or emulsion curing method), the chemical properties of the catalyst are the same.

[0108] In the precipitation method, the solution of step a) is combined with at least one transition metal compound in step b), and the entire reaction mixture is maintained at a temperature of at least 50 °C, more preferably in the temperature range of 55 to 110 °C, more preferably in the range of 70 to 100 °C, to ensure that the catalyst components are precipitated sufficiently in the form of solid catalyst component particles (step c).

[0109] In the emulsion solidification process, in step b), the solution of step a) is generally added to at least one transition metal compound at a relatively low temperature, for example, from -10°C to below 50°C, preferably from -5°C to 30°C. During the stirring of the emulsion, the temperature is generally maintained at -10°C to below 40°C, preferably from -5°C to 30°C. The droplets of the dispersed phase of the emulsion form an active catalyst composition. The solidification of the droplets (step c) is suitably carried out by heating the emulsion to a temperature of 70 to 150°C, preferably 80 to 110°C. The present invention preferably uses a catalyst prepared by the emulsion solidification process.

[0110] In step a), preference is given to using a solution of a2) or a3), ie a solution of (Ax') or a solution of a mixture of (Ax) and (Bx).

[0111] Preferably, the Group 2 metal is magnesium. The alkoxymagnesium compounds (Ax), (Ax'), (Bx) can be prepared in situ in the first step (step a) of the catalyst preparation process by reacting the magnesium compound with an alcohol as described above. Another option is to prepare the alkoxymagnesium compounds separately, or they can even be commercially available as pre-prepared alkoxymagnesium compounds and used as such in the catalyst preparation process of the present invention.

[0112] Illustrative examples of alcohol (A) are glycol monoethers. Preferred alcohols (A) are C2 to C4 glycol monoethers in which the ether group contains 2 to 18 carbon atoms, preferably 4 to 12 carbon atoms. Preferred examples are 2-(2-ethylhexyloxy)ethanol, 2-butoxyethanol, 2-hexyloxyethanol, 1,3-propylene glycol monobutyl ether, 3-butoxy-2-propanol, and 2-(2-ethylhexyloxy)ethanol, with 1,3-propylene glycol monobutyl ether and 3-butoxy-2-propanol being particularly preferred.

[0113] An exemplary monohydric alcohol (B) is represented by the structural formula ROH, wherein R is a linear or branched C2-C 16 Alkyl residue, preferably C4-C 10 The most preferred monohydric alcohol is 2-ethyl-1-hexanol or octanol.

[0114] Preferably, a mixture of alkoxymagnesium compounds (Ax) and (Bx) or a mixture of alcohols (A) and (B), respectively, is used, with a molar ratio of Bx:Ax or B:A of 10:1 to 1:10, more preferably 6:1 to 1:6, still more preferably 5:1 to 1:3, most preferably 5:1 to 3:1.

[0115] The alkoxymagnesium compound may be the reaction product of an alcohol as defined above and a magnesium compound selected from the group consisting of dialkylmagnesium, alkylmagnesium alkoxides, dialkoxymagnesium, alkoxymagnesium halides and alkylmagnesium halides. In addition, dialkoxymagnesium, diaryloxymagnesium, aryloxymagnesium halides, aryloxymagnesium and alkylaryloxymagnesium may also be used. The alkyl groups in the magnesium compound may be the same or different C1-C 20 Alkyl, preferably C2-C 10 Alkyl. When used, typical alkyl-alkoxy magnesium compounds are ethyl butoxy magnesium, butyl magnesium pentoxide, octyl butoxy magnesium and octyl magnesium octoxide. Dialkyl magnesium is preferably used. The most preferred dialkyl magnesium is butyl octyl magnesium or butyl ethyl magnesium.

[0116] In addition to alcohols (A) and (B), magnesium compounds can also react with alcohols of the formula R" (OH) m The polyol (C) is reacted with the alkoxy magnesium compound to obtain the alkoxy magnesium compound. If used, the preferred polyol is wherein R "is a linear, cyclic or branched C2 to C 10 An alcohol wherein m is an integer from 2 to 6 and a hydrocarbon residue.

[0117] Thus, the alkoxymagnesium compound of step a) is selected from dialkoxymagnesiums, diaryloxymagnesiums, alkoxymagnesium halides, aryloxymagnesium halides, alkylmagnesium alkoxides, arylalkoxymagnesiums and alkylaryloxymagnesiums or a mixture of magnesium dihalides and dialkoxymagnesiums.

[0118] The solvent used to prepare the catalyst can be selected from aromatic and aliphatic straight-chain, branched and cyclic hydrocarbons having 5 to 20 carbon atoms, more preferably 5 to 12 carbon atoms, or mixtures thereof. Suitable solvents include benzene, toluene, cumene, xylene, pentane, hexane, heptane, octane and nonane. Hexane and pentane are particularly preferred.

[0119] The reaction for preparing the alkoxymagnesium compound can be carried out at a temperature of 40 to 70° C. Those skilled in the art know how to select the most suitable temperature depending on the Mg compound and alcohol used.

[0120] The transition metal (TM) compound of Groups 4 to 6 as defined in the IUPAC 2013 edition is preferably a titanium compound, most preferably a titanium halide such as TiCl4.

[0121] The non-phthalic internal electron donor (ID) used to prepare the specific type of Ziegler-Natta catalyst used in the present invention is preferably selected from the group consisting of (diesters), 1,3-diethers, derivatives, and mixtures thereof of non-phthalic (di)acids. Particularly preferred electron donors are diesters of monounsaturated non-phthalic dicarboxylic acids, in particular from the group comprising malonates, maleates, succinates, citrates, glutarates, cyclohexene-1,2-dicarboxylates, and benzoates, and derivatives and / or mixtures thereof. Preferred examples are, for example, substituted maleates and citrates, with citrates being most preferred.

[0122] Here and hereinafter the term derivative includes substituted compounds.

[0123] In the emulsion solidification process, the two-phase liquid-liquid system can be formed by simple stirring and optionally adding (additional) solvents and / or additives, such as turbulence minimizing agents (TMA) and / or emulsifiers and / or emulsion stabilizers, such as surfactants, which are used in a manner known in the art. These solvents and / or additives are used to promote the formation of the emulsion and / or stabilize the emulsion. Preferably, the surfactant is an acrylic or methacrylic polymer. Particularly preferred are unbranched C 12 to C 20 (Meth)acrylates, such as poly(hexadecyl)-methacrylate and poly(octadecyl)-methacrylate, and mixtures thereof. If used, the turbulence minimizing agent (TMA) is preferably selected from polymers of α-olefin monomers having 6 to 20 carbon atoms, such as polyoctene, polynonene, polydecene, polyundecene, or polydodecene, or mixtures thereof. Most preferred is polydecene.

[0124] The solid particulate product obtained by precipitation or emulsion solidification can be washed at least once, preferably at least twice, and most preferably at least three times. The washing can be carried out with aromatic and / or aliphatic hydrocarbons, preferably with toluene, heptane or pentane. The washing can also be optionally carried out with aromatic and / or aliphatic hydrocarbons in combination with TiCl4. The washing liquid can also contain an electron donor and / or a Group 13 compound, such as a trialkylaluminum, a haloalkylaluminum compound or an alkoxyaluminum compound. The aluminum compound can also be added during the catalyst synthesis process. The catalyst can be further dried, for example by evaporation or purging with nitrogen, or it can be slurried into an oily liquid without any drying step.

[0125] The Ziegler-Natta catalyst of the particular type finally obtained ideally has particles with an average particle size ranging from 5 to 200 μm, preferably from 10 to 100 μm. The particles are generally dense, have low porosity, and generally have a particle size of less than 20 g / m 2 , more preferably less than 10g / m 2Typically, the content of Ti in the catalyst is in the range of 1 to 6 wt%, the content of Mg is in the range of 10 to 20 wt%, and the content of internal electron donor in the catalyst is in the range of 10 to 40 wt% of the catalyst composition. Detailed descriptions of the preparation of the catalyst used in the present invention are disclosed, for example, in WO2012 / 007430, EP2610271, and EP2610272.

[0126] An external electron donor (ED) is preferably present as an additional component in the polymerization process of the present invention. Suitable external electron donors (ED) include certain silanes, ethers, esters, amines, ketones, heterocyclic compounds and mixtures thereof. Particular preference is given to using silanes. Most preferably, silanes of formula (I) are used.

[0127] R a p R b q Si(OR c ) (4-p-q) (I)

[0128] where R a 、R b and R c represents a hydrocarbon group, in particular an alkyl group or a cycloalkyl group, and wherein p and q are numbers ranging from 0 to 3 and their sum (p+q) is equal to or less than 3. R a 、R b and R c Can be selected independently of each other and can be the same or different. Specific examples of silanes according to formula (I) are (tert-butyl)2Si(OCH3)2, (cyclohexyl)(methyl)Si(OCH3)2, (phenyl)2Si(OCH3)2 and (cyclopentyl)2Si(OCH3)2. Another most preferred silane is according to formula (II)

[0129] Si(OCH2CH3)3(NR 3 R 4 ) (II)

[0130] where R 3 and R 4 can be the same or different and represent a straight chain, branched chain or cyclic hydrocarbon group having 1 to 12 carbon atoms. 3 and R 4 Independently selected from methyl, ethyl, n-propyl, n-butyl, octyl, decyl, isopropyl, isobutyl, isopentyl, tert-butyl, tert-pentyl, neopentyl, cyclopentyl, cyclohexyl, methylcyclopentyl and cycloheptyl. Ethyl is most preferably used.

[0131] Typically, in addition to the Ziegler-Natta catalyst or the specific type of Ziegler-Natta catalyst and the optional external electron donor (ED), a cocatalyst (Co) may also be present in the polymerization process of the present invention. The cocatalyst is preferably a compound of Group 13 of the Periodic Table (IUPAC, 2013 edition), such as an aluminum compound, such as an organoaluminum or aluminum halide compound. The example of a suitable organoaluminum compound is an alkylaluminum or an alkylaluminum halide compound. In a particular embodiment, the cocatalyst (Co) is a trialkylaluminum, such as triethylaluminum (TEAL), dialkylaluminum chloride or alkylaluminum dichloride or a mixture thereof. In a particular embodiment, the cocatalyst (Co) is triethylaluminum (TEAL).

[0132] Typically, the molar ratio [Co / ED] between the cocatalyst (Co) and the external electron donor (ED) and / or the molar ratio [Co / TM] between the cocatalyst (Co) and the transition metal (TM) is carefully selected for each process. A suitable molar ratio [Co / ED] between the cocatalyst (Co) and the external electron donor (ED) may be in the range of 2.5 to 50.0 mol / mol, preferably in the range of 4.0 to 35.0 mol / mol, more preferably in the range of 5.0 to 30.0 mol / mol. A suitable lower limit may be 2.5 mol / mol, preferably 4.0 mol / mol, more preferably 5.0 mol / mol. A suitable upper limit may be 50.0 mol / mol, preferably 35.0 mol / mol, more preferably 30.0 mol / mol. The lower and upper values ​​of the ranges are inclusive.

[0133] A suitable molar ratio [Co / TM] between the cocatalyst (Co) and the transition metal (TM) may be in the range of 20.0 to 500.0 mol / mol, preferably in the range of 50.0 to 400.0 mol / mol, more preferably in the range of 100.0 to 300.0 mol / mol. A suitable lower limit may be 20.0 mol / mol, preferably 50.0 mol / mol, more preferably 100.0 mol / mol. A suitable upper limit may be 500.0 mol / mol, preferably 400.0 mol / mol, more preferably 300.0 mol / mol. The lower and upper limits of the ranges are inclusive.

[0134] Hindered amine light stabilizers

[0135] The polypropylene composition of the present invention comprises at least one hindered amine light stabilizer. Those skilled in the art will appreciate that hindered amine light stabilizers (HALS) are well-known additives in polymer chemistry. Hindered amine light stabilizers (HALS) are compounds containing amine functional groups that are used as stabilizers, and detailed information has been published elsewhere, for example in Zweifel, Hans; Maier, Ralph D.; Schiller, Michael (2009). Handbook of Plastic Additives (6th ed.). Munich: Hanser. These compounds are typically 2,2,6,6-tetramethyl-piperidine derivatives containing at least one group of formula (I):

[0136]

[0137] wherein R1 and R2 are optionally substituted organic substituents independently selected from hydrogen, hydroxyl, linear or branched alkyl, linear or branched alkenyl, aryl, linear or branched amine, linear or branched carboxyl, linear or branched ester, and linear or branched ether; and

[0138] Rx is hydrogen or methyl.

[0139] Example structures of suitable hindered amine light stabilizers include:

[0140]

[0141]

[0142] where R' is

[0143]

[0144]

[0145]

[0146] Where R'=R" or H,

[0147] And among them

[0148]

[0149]

[0150]

[0151] Generally, the hindered amine light stabilizers are classified according to their molecular weight, i.e., a high molecular weight hindered amine light stabilizer is one with Mw > 2000 g / mol, and a low molecular weight hindered amine light stabilizer is one with Mw below 1000. Preferably, the at least one hindered amine light stabilizer used in the composition of the present invention is a high molecular weight hindered amine light stabilizer.

[0152] Suitable hindered amine light stabilizers for use in the present invention are listed in the literature, for example, in Zweifel, Hans; Maier, Ralph D.; Schiller, Michael (2009). Handbook of Plastic Additives (6th ed.). Munich: Hanser, pp. 123-136. Among them, the most suitable high molecular weight hindered amine light stabilizers are Tinuvin 622 (polymer of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinol, CAS 65447-77-0) and Chimassorb 944 (poly((6-((1,1,3,3-tetramethylbutyl)amino)-1,3,5-triazine-2,4-diyl)(2,2,6,6-tetramethyl-4-piperidinyl)imino)-1,6-hexanediyl((2,2,6,6-tetramethyl-4-piperidinyl)imino), CAS 71878-19-8) and low molecular weight hindered amine light stabilizers are ADK STAB LA-82 (CAS 68548-08-3) and ADK STAB LA-87 (2,2,6,6-tetramethyl-4-piperidinyl methacrylate, CAS 31582-45-3), the structure is as follows:

[0153]

[0154] In one embodiment, the at least one hindered amine light stabilizer is preferably a compound represented by the following general formula (II):

[0155]

[0156] in

[0157] X is O, NH or NR 3 , where R 3 is a C1-C8 alkyl group;

[0158] R 4 、R 5 and R 6 independently selected from H, C1-C8 alkyl, C1-C8 alkenyl and optionally substituted C6-C 12 aryl; and

[0159] R 7 H, C1-C8 alkyl, C6-C 12 Cycloalkyl, C1-C10 Acyl, C1-C 10 Acyloxy or C1-C8 alkyl ether;

[0160] Among them, C6-C 12 Optional substituents on the aryl group are C1-C8 hydrocarbon groups, such as C1-C8 alkyl groups or C1-C8 alkenyl groups.

[0161] Preferably, in formula (II), X=O, R 4 and R 5 H, R 6 is H or methyl and R 7 is H, C1-C8 alkyl, such as methyl, or C1-C9 acyl, such as acetyl or acetoxy.

[0162] ADK STAB LA-87 (structure as above) is a particularly preferred example of a hindered amine light stabilizer of formula (II).

[0163] The composition of the present invention may contain a single hindered amine light stabilizer, or a mixture of two or more hindered amine light stabilizers.

[0164] In a preferred embodiment, the composition of the present invention comprises a single hindered amine light stabilizer, which is a high molecular weight hindered amine light stabilizer as defined above, such as Tinuvin 622 (CAS 65447-77-0).

[0165] In another preferred embodiment, the composition of the invention comprises a mixture of two hindered amine light stabilizers, in particular at least one of which comprises at least one group of formula (I) as defined above, or at least one of which is a compound of formula (II) as defined above.

[0166] When the composition of the present invention comprises a mixture of two hindered amine light stabilizers, it is particularly preferred that at least one is a high molecular weight hindered amine light stabilizer as defined above, and even more preferred that one of them is a high molecular weight hindered amine light stabilizer and the other is a compound of general formula (II) as defined above.

[0167] Relative to the total weight of the polypropylene composition, at least one hindered amine light stabilizer is typically present in an amount of 0.05 to 0.5 wt%, preferably 0.1 to 0.45 wt%, more preferably 0.15 to 0.4 wt%. It should be understood that when more than one hindered amine light stabilizer is present, these weight % ranges apply to the total amount of all hindered amine light stabilizers.

[0168] Polypropylene composition

[0169] It is also within the scope of the present invention that the polypropylene composition comprises other polymers in addition to the bimodal random Ziegler-Natta propylene copolymer, preferably the bimodal random Ziegler-Natta propylene copolymer is the only polymer component in the polypropylene composition. It should be understood that the polymer composition may also contain standard polymer additives (which may be part of a masterbatch).

[0170] Besides the bimodal random copolymer and the at least one hindered amine light stabilizer the polypropylene composition of the present invention may comprise further additives.

[0171] Examples of such additives include, but are not limited to, stabilizers such as antioxidants (e.g., hindered phenols, phosphites / phosphonites, alkyl radical scavengers, aromatic amines, or mixtures thereof), metal deactivators (e.g., MD 1024) or UV stabilizers. Other typical additives are modifiers, such as antistatic agents or antifogging agents (for example ethoxylated amines and amides or glycerides), acid scavengers (for example calcium stearate), blowing agents, adhesives (for example polyisobutylene), lubricants and resins (for example ionomer waxes, polyethylene and ethylene copolymer waxes, Fischer-Tropsch waxes, montan waxes, fluorine-based compounds or paraffin waxes), as well as slip agents and anti-blocking agents (for example erucamide, oleamide, talc, natural and synthetic silica or zeolites) and mixtures thereof.

[0172] Generally speaking, the total amount of the additives is in the range of 0.1 to 5.0 wt%, preferably in the range of 0.1 to 2.0 wt%, more preferably in the range of 0.1 to 1.5 wt%.The amount of the additives is relative to the total amount of the polypropylene composition.

[0173] In a particularly preferred embodiment, the polypropylene composition of the present invention further comprises at least one α-nucleating agent. The α-nucleating agent may be present in an amount ranging from 0.01 to 1.0 wt. %, preferably in an amount ranging from 0.03 to 0.9 wt. %, more preferably in an amount ranging from 0.05 to 0.8 wt. %. The amount of the at least one α-nucleating agent is relative to the total amount of the polypropylene composition of the present invention.

[0174] The α-nucleating agent is generally selected from the group consisting of:

[0175] (i) salts of monocarboxylic and polycarboxylic acids, for example sodium benzoate or aluminum tert-butylbenzoate,

[0176] (ii) dibenzylidene sorbitol (for example 1,3:2,4-dibenzylidene sorbitol) and C1-C8-alkyl-substituted dibenzylidene sorbitol derivatives, for example methyldibenzylidene sorbitol, ethyldibenzylidene sorbitol or dimethyldibenzylidene sorbitol (for example 1,3:2,4-bis(methylbenzylidene) sorbitol), or substituted nonanol derivatives, for example 1,2,3-trideoxy-4,6:5,7-bis-O-[(4-propylphenyl)methylene]-nonanol,

[0177] (iii) salts of phosphoric acid diesters, for example sodium 2,2'-methylenebis(4,6-di-tert-butylphenyl)phosphate or hydroxyaluminum-bis[2,2'-methylene-bis(4,6-di-tert-butylphenyl)phosphate],

[0178] (iv) vinylcycloalkane polymers and vinylalkane polymers, and

[0179] (v) mixtures thereof.

[0180] Preferably, the α-nucleating agent is dibenzylidene sorbitol (e.g. 1,3:2,4-dibenzylidene sorbitol) or a C1-C8-alkyl-substituted dibenzylidene sorbitol derivative, such as methyldibenzylidene sorbitol, ethyldibenzylidene sorbitol or dimethyldibenzylidene sorbitol (e.g. 1,3:2,4-di(methylbenzylidene)sorbitol) or a substituted nonanol derivative, such as 1,2,3,-trideoxy-4,6:5,7-bis-O-[(4-propylphenyl)methylene]-nonanol.

[0181] Typically, the nucleating agent is present in the polypropylene composition in an amount of 50 to 6000 ppm, preferably 100 to 5000 ppm, more preferably 200 to 4000 ppm, such as 1200 to 3000 ppm.

[0182] As stated above, the polypropylene composition of the present invention is typically prepared by extruding a bimodal random copolymer in the presence of at least one hindered amine light stabilizer and any other optional components.

[0183] At the end of the extruder, a polypropylene composition melt is obtained. The polypropylene composition melt of the present invention can then pass through the die in the optional die zone of the extruder. When the polypropylene composition melt of the present invention passes through the die, it is usually further cooled and pelletized.

[0184] The die area typically comprises a die plate, which is typically a thick metal disk with a plurality of holes. These holes are parallel to the screw axis.

[0185] The pelletizer is generally a chain pelletizer or an underwater pelletizer.

[0186] Generally speaking, the polypropylene composition of the present invention has a haze value of <20%, preferably 2% to 18%, more preferably 3% to 17%. The haze value is measured according to ASTM D1003 on injection molded plaques with a thickness of 1 mm produced according to EN ISO 18732.

[0187] Generally speaking, the polypropylene composition of the present invention has a melting temperature > 150° C., such as in the range of 150 to 165° C., preferably in the range of 150 to 162° C. The melting temperature (Tm) is measured by DSC according to ISO 11357 / 3.

[0188] Generally speaking, the polypropylene composition of the present invention has a crystallization temperature > 115° C., preferably in the range of 120 to 132° C., more preferably in the range of 123 to 130° C. The melting temperature (Tc) is measured by DSC according to ISO 11357 / 3.

[0189] Generally speaking, the polypropylene composition of the present invention has a xylene soluble content (XCS) in the range of 5.5 to 18.0 wt.-%, preferably in the range of 6.0 to 16.0 wt.-%, more preferably in the range of 6.5 to 15.0 wt.-%. The xylene soluble fraction is determined according to ISO 16152 at 25°C.

[0190] Generally speaking, the polypropylene composition of the present invention has a flexural modulus >900 MPa, preferably in the range of 950 to 1600 MPa, more preferably in the range of 1000 to 1600 MPa. The flexural modulus is measured according to ISO 178 at 23°C / 24h on injection molded test specimens.

[0191] Generally speaking, the polypropylene composition of the present invention has a strength of greater than 4.80 kJ / m 2 , preferably 4.85 to 20.00 kJ / m 2 The Charpy notched impact strength is measured according to ISO 179 / 1eA at 23°C on injection molded test specimens as described in EN ISO 1873-2.

[0192] application

[0193] The present invention also provides an article comprising the polypropylene composition of the present invention. Suitable articles are films, such as cast films, and injection molded articles. Preferred articles are closure caps, screw caps or closure systems for food or fluid packaging.

[0194] The invention will now be described with reference to the following non-limiting examples. BRIEF DESCRIPTION OF THE DRAWINGS

[0195] Figure 1 Notched impact strength measurements of CE1, IE1 and IE2 after gamma sterilization. DETAILED DESCRIPTION

[0196] I. Measurement Method

[0197] a) Melt flow rate

[0198] Melt flow rate (MFR) is measured according to ISO 1133 and expressed in g / 10 min. MFR is an indicator of a polymer's flowability and processing properties. The higher the melt flow rate, the lower the polymer's viscosity. The MFR2 of polypropylene is measured at 230°C and a load of 2.16 kg.

[0199] b) DSC analysis

[0200] Melting and crystallization temperatures were measured on 5 to 10 mg samples using a TA Instrument Q2000 differential scanning calorimeter (DSC) in accordance with ISO 11357 / 3 under a 50 mL / min nitrogen atmosphere. Crystallization and melting temperatures were obtained using a heat / cool / heat cycle with a scan rate of 10°C / min over a temperature range of 30°C to 225°C. The crystallization and melting temperatures were measured as the endothermic peak and exothermic peak, respectively, during the cooling and second heating steps.

[0201] c) Xylene soluble content (XCS, wt%)

[0202] The xylene-soluble polymer content is determined according to ISO 16152; 5th edition; 1 July 2005, at 25°C.

[0203] d) Flexural modulus

[0204] Flexural modulus is measured according to ISO 178 at 23°C.

[0205] e) Charpy notch impact

[0206] The Charpy notched impact strength is determined according to ISO 179 / 1eA at 23° C. on injection molded test specimens as described in EN ISO 1873-2 (80×10×4 mm).

[0207] f) Haze

[0208] Haze according to ASTM D1003 on a 60x60mm thick plate produced according to EN ISO 1873-2 with a thickness of 1mm 2 The results were measured on injection molded plates.

[0209] g) Comonomer content

[0210] Poly(propylene-co-ethylene) - Determination of ethylene content by infrared spectroscopy

[0211] Quantitative infrared (IR) spectroscopy was used to quantify the ethylene content of poly(ethylene-co-propylene) copolymers by calibration to the primary method.

[0212] Calibration is facilitated by using a set of in-house non-commercial calibration standards that are quantitatively 13 The known ethylene content was determined by solution-state nuclear magnetic resonance (NMR) spectroscopy. The calibration procedure was performed according to conventional methods well documented in the literature. The calibration set consists of 38 calibration standards with ethylene contents ranging from 0.2 to 75.0 wt%, produced under various conditions at pilot or full-scale. The calibration set was selected to reflect the typical copolymer species encountered in the final quantitative infrared spectroscopy method.

[0213] Quantitative infrared spectra were recorded in the solid state using a Bruker Vertex 70 FTIR spectrometer. Spectra were recorded on 25 × 25 mm square films with a thickness of 300 μm, prepared by compression molding, at 180–210°C and 4–6 mPa. For samples with very high ethylene content (>50 mol%), 100 μm thick films were used. Standard transmission FTIR spectroscopy was employed in the spectral range of 5000–500 cm -1 , aperture is 6mm, spectral resolution is 2cm -1 , 16 background scans, 16 spectral scans, an interferogram zero-filling factor of 64 and Blackmann-Harris three-term apodization.

[0214] Use the corresponding (CH2) >2 730 and 720cm of the structural unit -1 (A Q ) to quantitatively analyze the total area of ​​CH2 rocking deformation at 762 and 694 cm -1 The quantification band was normalized to 4323 cm corresponding to the CH structural unit. -1 (A R ) at the CH band area (integration method G, limit 4650, 4007cm -1 Then, a secondary calibration curve was used to normalize the absorbance (A Q / A R ) to predict the ethylene content in weight percent. The calibration curve had been previously constructed by ordinary least squares (OLS) regression of the normalized absorbance measured on the calibration device and the main comonomer content. 13 Poly(propylene-co-ethylene)-ethylene content calibrated by C NMR spectroscopy

[0215] Quantitative measurements were recorded in solution using a Bruker Avance III 400 NMR spectrometer. 13 C{ 1 H} NMR spectra, 1H and 13C spectra were run at 400.15 and 100.62 MHz, respectively. All spectra were recorded at 125°C using a 13C-optimized 10 mm extended temperature probe and nitrogen was used for all pneumatics. Approximately 200 mg of material was dissolved in 3 ml of 1,2-tetrachloroethane-d2 (TCE-d2) along with chromium (III) acetylacetonate (Cr(acac)3) to form a 65 mM relaxation agent solution (Singh, G., Kothari, A., Gupta, V., Polymer Testing 28 5 (2009), 475). To ensure a homogeneous solution, the NMR tube was further heated in a rotary oven for at least 1 hour after the initial sample was prepared in a heating block. After insertion of the magnet, the tube was rotated at a speed of 10 Hz. This apparatus was chosen primarily for the high resolution and quantitative properties required for accurate determination of ethylene content. Standard single pulse excitation without NOE was used with an optimized tip angle, 1 s recycle delay, and a two-level WALTZ16 decoupling scheme (Zhou, Z., Kuemmerle, R., Qiu, X., Redwine, D., Cong, R., Taha, A., Baugh, D. Winniford, B., J. Mag. Reson. 187 (2007) 225, Busico, V., Carbonniere, P., Cipullo, R., Pellecchia, R., Severn, J., Talarico, G., Macromol. Rapid Commun. 2007, 28, 1128). A total of 6144 (6k) transients were collected for each spectrum. 13 C{ 1 The H} NMR spectra were processed, integrated, and the relevant quantitative properties were determined from the integration. All chemical shifts were indirectly referenced to the central methylene of the ethylene block (EEE) at 30.00 ppm using the chemical shift of the solvent. This method allows for comparable referencing even in the absence of this structural unit. Characteristic signals corresponding to ethylene incorporation were observed (Cheng, HN, Macromolecules 17 (1984), 1950), and the comonomer composition was calculated as the fraction of ethylene in the polymer relative to all monomers in the polymer: fE = (E / (P+E). The comonomer composition was quantified using the method of Wang et al. (Wang, WJ., Zhu, S., Macromolecules 33 (2000), 1157) by integration 13 C{ 1H} spectrum. This approach was chosen for its robust nature and its ability to account for the presence of regional defects when required. The integration regions were slightly adjusted to improve applicability over the entire range of comonomer contents encountered. For systems with very low ethylene contents, where only isolated ethylene is observed in the PPEPP sequence, the method of Wang et al. was modified to reduce the impact of integration of sites that are no longer present. This approach reduces the overestimation of ethylene content for such systems and is achieved by reducing the number of sites used to determine the absolute ethylene content to E = 0.5(Sββ + Sβγ + Sβδ + 0.5(Sαβ + Sαγ)). The corresponding integration equation for this set of sites becomes E = 0.5(I H +I G +0.5(I C +I D ), using the same symbols as used in Wang et al. (Wang, WJ., Zhu, S., Macromolecules 33 (2000), 1157). The equation for absolute propylene content was not modified. The mole percent comonomer incorporation was calculated from the mole fraction: E [mol%] = 100 * fE. The weight percent comonomer incorporation was calculated from the mole fraction: E [weight%] = 100 * (fE * 28.06) / ((fE * 28.06) + ((1 - fE) * 42.08)).

[0216] h) Total migration (OM)

[0217] Total migration according to EN 1SO 1186-14:2002 in 60x60x1mm 3 Measured on injection molded plaques.

[0218] i) Gamma sterilization

[0219] Prepared according to EN ISO 1873-2 80x10x4 mm 3 Charpy injection molded test specimens were exposed to 50 kGy of gamma radiation using a 60Co gamma ray source. As shown below, the samples were aged continuously in a circulating air oven at 80°C for up to 60 days. After the required time, the samples were removed from the oven and aged at 23°C for 24 hours before impact testing according to ISO 179 / 1eA+23°C.

[0220] II. Examples and Comparative Examples

[0221] a) Catalyst Preparation

[0222] To prepare the catalyst, 3.4 liters of 2-ethylhexanol and 810 mL of propylene glycol butyl monoether (4 / 1 molar ratio) were added to a 20.0 L reactor. 7.8 liters of a 20.0% BEM (butylethylmagnesium) toluene solution, supplied by Crompton GmbH, were then slowly added to the well-stirred alcohol mixture. During the addition, the temperature was maintained at 10.0°C. Following the addition, the temperature of the reaction mixture was raised to 60.0°C, and mixing continued at this temperature for 30 minutes. Finally, after cooling to room temperature, the resulting magnesium alkoxide was transferred to a storage container.

[0223] 21.2 g of the magnesium alkoxide prepared above was mixed with 4.0 ml of bis(2-ethylhexyl) citrate for 5 minutes. After mixing, the resulting magnesium complex was immediately used in the preparation of the catalyst component.

[0224] At 25.0°C, 19.5 ml of titanium tetrachloride was placed in a 300 ml reactor equipped with a mechanical stirrer. The mixing speed was adjusted to 170 rpm. 26.0 g of the magnesium complex prepared above was added over 30 minutes while maintaining the temperature at 25.0°C. 3.0 ml of 1-254 and 1.0 ml contains 2 mg Necadd 447 TM A toluene solution of 1% ethanol was added. 24.0 ml of heptane was then added to form an emulsion. Mixing was continued at 25.0°C for 30 minutes, after which the reactor temperature was raised to 90.0°C over 30 minutes. The reaction mixture was stirred at 90.0°C for an additional 30 minutes. Stirring was then stopped and the reaction mixture was allowed to stand at 90.0°C for 15 minutes. The solid material was washed five times: at 80.0°C with stirring at 170 rpm for 30 minutes. After stopping stirring, the reaction mixture was allowed to stand for 20-30 minutes and then siphoned.

[0225] Wash 1: Wash with a mixture of 100 ml of toluene and 1 ml of electron donor.

[0226] Wash 2: Wash with a mixture of 30 ml TiCl4 and 1 ml electron donor.

[0227] Wash 3: Wash with 100 ml of toluene.

[0228] Wash 4: Wash with 60 ml of heptane.

[0229] Wash 5: Wash with 60 ml of heptane for 10 minutes under stirring.

[0230] Then, the stirring was stopped and the reaction mixture was allowed to stand for 10 minutes while the temperature was lowered to 70° C., followed by siphoning and then sparging with N 2 for 20 minutes to obtain a gas-sensitive powder.

[0231] b) Embodiments of the present invention (IE1 and IE2)

[0232] Both the comparative composition and the inventive composition comprised a bimodal random propylene copolymer produced in a pilot plant comprising a prepolymerisation reactor, a slurry loop reactor and a gas phase reactor using the above-described solid catalyst component, triethylaluminium (TEAL) as a cocatalyst and dicyclopentyldimethoxysilane (D-donor) as an external electron donor.

[0233] The properties of the polymer are controlled by the ethylene polymer produced in each reactor, the MFR, and the split between reactors. To obtain the desired polymer, the concentrations of H2 and C2 are appropriately adjusted. Typical polymerization process conditions and properties of bimodal random propylene copolymers are shown in Table 1.

[0234] The inventive and comparative polypropylene compositions were prepared in a Coperion ZSK 40 (screw diameter 40 mm, L / D ratio 38) co-rotating twin-screw extruder by extruding a bimodal random propylene copolymer with the additives shown in Table 2. The temperature in the extruder was in the range of 190-230°C.

[0235] After the extrusion step and after solidification of the linear form in a water bath, the obtained polypropylene composition is pelletized in an in-line pelletizer.

[0236] The properties of the polypropylene compositions are described in Table 2.

[0237] The LDPE is MA8200, which is commercially available from Borealis AG, Austria. It has an MFR2 (190°C) of 7.5 g / 10 min and a density of 920 kg / m 3 .

[0238] AS is calcium stearate (CEASIT FI), supplied by Baerlocher, Germany;

[0239] The antioxidant was tris(2,4-di-tert-butylphenyl)phosphite (Irgafos 168), supplied by BASF AG, Germany;

[0240] The hindered amine light stabilizer HALS1 is Tinuvin 622, an oligomeric piperidine-type hindered amine light stabilizer supplied by BASF, Germany;

[0241] The hindered amine light stabilizer HALS2 is ADK STAB LA-87, a polymerizable methacrylate type hindered amine light stabilizer provided by ADEKA Corporation of Japan;

[0242] The nucleating agent was 1,3:2,4-bis(3,4-dimethylbenzylidene) sorbitol (Millad 3988), purchased from Milliken, USA.

[0243] Table 1 Polymerization process conditions and properties of bimodal random propylene copolymer

[0244]

[0245]

[0246] *Split is related to the amount of propylene polymer produced in each specific reactor.

[0247] Table 2 Composition and properties of polypropylene.

[0248]

[0249] *Measurements were performed on pellets obtained after the extrusion process.

[0250] As can be gathered from Table 2, the polypropylene compositions (inventive examples) show a balanced combination of high flow, high stiffness and impact properties as well as a high level of optical properties (low haze values).

[0251] The notched impact strength measurement results after gamma sterilization are as follows Figure 1 The inventive examples had higher toughness after sterilization and over the entire test time range, indicating that they have improved gamma sterilization stability.

Claims

1. A polypropylene composition comprising: a) a bimodal random Ziegler-Natta propylene copolymer having a comonomer content of 2.0 to 4.5 wt%, said copolymer comprising: (i) 30 to 70 wt% of a first propylene copolymer having a comonomer content in the range of 0.1 to 4.5 wt%, relative to the total weight of the first propylene copolymer, and an MFR2 of 1 to 100 g / 10 min; and (ii) 70 to 30 wt% of a second propylene copolymer having a comonomer content in the range of 1.0 to 15 wt%, relative to the total weight of the second propylene copolymer, and an MFR2 of 1 to 100 g / 10 min; with the proviso that the comonomer content of the second propylene copolymer (ii) is higher than the comonomer content of the first propylene copolymer (i); and b) at least one hindered amine light stabilizer.

2. The polypropylene composition according to claim 1, wherein the first propylene copolymer (i) and / or the second propylene copolymer (ii) is a copolymer of propylene and at least one comonomer selected from ethylene and C4-C10 α-olefins.

3. The polypropylene composition according to claim 2, wherein the first propylene copolymer (i) and / or the second propylene copolymer (ii) is a copolymer of propylene and ethylene.

4. The polypropylene composition according to claim 1, wherein the bimodal random propylene copolymer is a copolymer of propylene and at least one comonomer selected from ethylene and C4-C10 α-olefins.

5. The polypropylene composition according to claim 4, wherein the bimodal random propylene copolymer is a copolymer of propylene and ethylene.

6. The polypropylene composition according to claim 1, wherein at least one of the hindered amine light stabilizers is a compound containing at least one group of formula (I): in, R1 and R2 are optionally substituted organic substituents; and Rx is hydrogen or methyl.

7. The polypropylene composition according to claim 6, wherein R1 and R2 of formula (I) are independently selected from hydrogen, hydroxyl, linear or branched alkyl, linear or branched alkenyl, aryl, linear or branched amine, linear or branched carboxylic acid, linear or branched ester and linear or branched ether.

8. The polypropylene composition according to claim 1, wherein at least one of the hindered amine light stabilizers is a compound of formula (II) as shown below: in X is O, NH or NR 3 , where R 3 is a C1-C8 alkyl group; R 4 、R 5 and R 6 independently selected from H, C1-C8 alkyl, C1-C8 alkenyl and optionally substituted C6-C 12 aryl; and R 7 H, C1-C8 alkyl, C6-C 12 Cycloalkyl, C1-C 10 Acyl, C1-C 10 Acyloxy or C1-C8 alkyl ether; in, The C6-C 12 Optional substituents on the aryl group are C1-C8 hydrocarbon groups.

9. The polypropylene composition of claim 1, wherein the composition comprises a mixture of two hindered amine light stabilizers.

10. The polypropylene composition according to claim 1, wherein the molecular weight Mw of at least one hindered amine light stabilizer is > 2000 g / mol. The polypropylene composition according to claim 1 , further comprising an α-nucleating agent.

12. The polypropylene composition according to claim 1, wherein the bimodal random propylene copolymer has an MFR2 of 1.0 to 60 g / 10 min.

13. The polypropylene composition of claim 1, wherein the composition has a melting temperature (Tm) of 150 to 165°C.

14. The polypropylene composition of claim 1, wherein the composition is gamma sterilizable.

15. A method for preparing the polypropylene composition according to claim 1, comprising the steps of: a) in a first reactor, polymerizing propylene and one or more selected from ethylene and C4-C 10 a monomer containing a comonomer of an α-olefin to obtain a first propylene polymer component having a comonomer content in the range of 0.1 to 4.5 wt%, b) in a second reactor, polymerizing a mixture comprising propylene and one or more selected from ethylene and C4-C 10 a monomer containing a comonomer of an α-olefin to obtain a second propylene polymer component having a comonomer content in the range of 1.0 to 15 wt%, c) extruding the polymer component in the presence of at least one hindered amine light stabilizer; The polymerization is carried out in the presence of a Ziegler-Natta catalyst.

16. The method for preparing the polypropylene composition according to claim 15, wherein: The first reactor is a slurry reactor, and / or the second reactor is a gas phase reactor.

17. The method of claim 15, wherein the Ziegler-Natta catalyst does not contain phthalic acid compounds.

18. The process of claim 15, wherein the process is operated in the presence of a Ziegler-Natta catalyst having a transition metal from Groups 4 to 6 of the Periodic Table, the catalyst comprising an internal electron donor, an optional cocatalyst, and an optional external electron donor, wherein the internal electron donor is a non-phthalic acid internal electron donor.

19. The method according to claim 18, wherein the non-phthalic internal electron donor is a (di)ester selected from non-phthalic carboxylic (di)acids, wherein the (di)ester belongs to the group comprising malonates, maleates, succinates, citrates, glutarates, cyclohexene-1,2-dicarboxylates and benzoates and their derivatives or mixtures thereof.

20. An article comprising the polypropylene composition according to claim 1.

21. The article of claim 20, wherein the article is a cast film, an injection molded article, a closure cap, a screw cap, or a closure system for food or fluid packaging.

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