EA042471B1 - METHOD FOR PRODUCING POLYPROPYLENE COMPOSITION - Google Patents

Description

The present invention relates to a method for producing a polypropylene composition by sequential polymerization. More specifically, the present invention relates to a method for preparing a polypropylene composition containing propylene and one or more comonomers selected from ethylene and C ₄ -C ₁₀ alpha-olefins, and to a polypropylene composition obtained using this method. The present invention also relates to an article containing a polypropylene composition.

Propylene homopolymers and copolymers are suitable for many applications such as packaging, textiles, automobiles and pipes. An important field of application for propylene homopolymers and copolymers is the packaging industry, in particular in the field of films and molding.

In the field of packaging, it is very important to have a well-flowing polypropylene composition with good mechanical properties, i.e. high tensile modulus and good impact strength. Good fluidity is necessary to achieve good machinability in various product manufacturing processes, such as injection molding, which allows high production speeds that are typically required in mass production markets. Mechanical properties are also important in this type of application, in particular in the field of containers in which it is necessary to contain contents such as foodstuffs or the liquid contained therein. In addition, there is a need for sufficient rigidity of the containers so that they can be stacked on top of each other.

In addition, the polypropylene composition must also withstand mechanical damage during compression, which usually occurs, for example, when products are dropped.

In addition, haze should also be acceptable. In particular, a good balance between hardness and haze is required.

However, at least some of these properties can only be achieved at the expense of other of these properties. For example, as the melt flow rate increases, the stiffness can be improved while the impact resistance properties are greatly reduced. Thus, the impact strength and the melt flow rate of the polypropylene composition behave in the opposite way.

In addition, the high degree of crystallinity of the polypropylene composition makes it rather stiff, however it also increases haze. Thus, the balance of stiffness and haze in the polypropylene composition is of great importance.

Thus, there is a general need for a process for the manufacture of a polypropylene composition that is characterized by a balanced combination of high flow, high stiffness and impact resistance, and a high level of optical properties (low haze value).

EP 2539398 describes a process for the production of a random propylene copolymer by sequential polymerization, comprising the steps

a) polymerization of propylene and at least one of ethylene and/or C ₄ -C ₂₀ α-olefin in the first reactor (R1) to obtain polypropylene (PP1), which is a random propylene copolymer (R-PP1), and the specified polypropylene ( PP1) has a melt flow rate MFR ₁₀ (230°C), measured in accordance with ISO 1133, not more than 1.5 g/10 min;

b) transferring the first polypropylene (PP1) to the second reactor (R2);

c) polymerizing in the second reactor (R2) and in the presence of said first polypropylene (PP1) propylene and optionally at least one of ethylene and/or C ₄ -C ₂₀ α-olefin, resulting in a second polypropylene (PP2), wherein said the first polypropylene (PP1) and said second polypropylene (PP2) form a (homogeneous) mixture, and said second polypropylene (PP2) is a first propylene homopolymer (H-PP1) or a second random propylene copolymer (R-PP2);

d) transferring the mixture of the first polypropylene (PP1) and the second polypropylene (PP2) to the third reactor (R3); And

e) polymerizing in a third reactor (R3) and in the presence of a mixture of a first polypropylene (PP1) and a second polypropylene (PP2) propylene and optionally at least one of ethylene and/or C ₄ -C ₂₀ α-olefin, resulting in a third polypropylene (PP3), wherein said third polypropylene (PP3) is a second propylene homopolymer (H-PP2) or a third random propylene copolymer (R-PP3), and a first polypropylene (PP1), a second polypropylene (PP2) and a third polypropylene (PP3) form a (homogeneous) mixture.

However, the invention described in EP 2539398 relates to pipes and thus the MFR ₂ of the resulting random propylene copolymer is between 0.5 and 10.0 g/10 min and it may contain, in particular, beta- nucleating agents. Furthermore, EP 2539398 is silent on the haze properties of the resulting random propylene copolymer.

The present invention is based on the fact that the above described needs for a balanced combination of high fluidity, high stiffness and impact resistance and high level of optical properties (low haze value) can be achieved by a process for preparing a particular polypropylene composition. Thus, in the present image, a method for obtaining a polypropylene composition by sequential polymerization is proposed, including the steps

a) polymerizing in a first reactor, preferably a slurry reactor, monomers comprising propylene and optionally one or more comonomers selected from ethylene and C ₄ -C ₁₀ alpha olefins, to obtain a first propylene polymer fraction with a comonomer content ranging from 0.0 to 1 .0 wt%;

b) polymerizing in a second reactor, preferably a first gas phase reactor, monomers comprising propylene and one or more comonomers selected from ethylene and C ₄ -C ₁₀ alpha-olefins in the presence of a first propylene polymer fraction to obtain a second propylene polymer fraction containing comonomer in the range from 0.3 to 2.0 wt.%;

c) polymerizing in a third reactor, preferably a second gas phase reactor, monomers comprising propylene and one or more comonomers selected from ethylene and C ₄ -C ₁₀ alpha-olefins in the presence of a second propylene polymer fraction to obtain a third propylene polymer fraction containing comonomer in the range from 1.5 to 5.0 wt.%;

d) extruding a third propylene polymer fraction in the presence of at least one alpha-nucleating agent, wherein the polypropylene composition has an MFR ₂ value in the range of 12.0 to 60.0 g/10 min, measured according to ISO 1133 at 230°C under load of 2.16 kg.

Fractions of the first, second and third propylene polymers according to the present invention are obtained using a sequential polymerization method. In the present application, the term sequential polymerization process indicates that the propylene polymer fractions are produced by a process comprising at least three reactors connected in series. In one preferred implementation in this application, the term method of sequential polymerization indicates that the reaction mixture of the first reactor, i. the fraction of the first propylene polymer with unreacted monomers is transferred, preferably directly transferred, to a second reactor in which a fraction of the second propylene polymer is obtained. The reaction mixture of the second reactor, i. the fraction of the second propylene polymer with unreacted monomers is transferred, preferably directly transferred, to a third reactor in which a fraction of the third propylene polymer is obtained

Accordingly, in the method according to the present invention

i) the fraction of the first propylene polymer obtained in the first reactor, usually contains the first propylene polymer, which is obtained in the specified first reactor, ii) the fraction of the second propylene polymer, obtained in the second reactor, usually contains the second propylene polymer, which is obtained in the specified second reactor, iii) the fraction of the third propylene polymer obtained in the third reactor, usually contains the third propylene polymer, which is obtained in the specified third reactor.

Accordingly, the method according to the present invention includes at least a first reactor, a second reactor and a third reactor. The method may include at least one additional polymerization reactor after the third reactor. In one specific embodiment, the process according to the present invention consists of three polymerization reactors, i.e. the first reactor, the second reactor and the third reactor. The term polymerization reactor indicates that the main polymerization takes place in it. Thus, if the process consists of three or more polymerization reactors, this definition does not exclude the possibility that the whole process includes, for example, a prepolymerization step in the prepolymerization reactor. The term consists of is only an indication of the presence of the main polymerization reactors. Where the process of the present invention generally comprises a prepolymerization reactor, the term first propylene polymer fraction means the total amount of (co)polymer produced in the prepolymerization reactor and (co)polymer produced in the first reactor.

The reactors are typically selected from slurry and gas phase reactors.

The first reactor is preferably a slurry reactor and can be any continuous or stirred batch reactor or loop reactor operating in bulk or slurry polymerization mode. By bulk polymerization is meant a process in which the polymerization is carried out in a liquid monomer substantially in the absence of an inert solvent. However, the person skilled in the art knows that the monomers used in industrial production are never pure and always contain aliphatic hydrocarbons as impurities. For example, propylene monomer may contain up to 5% propane as an impurity. Thus, bulk polymerization preferably means polymerization in a reaction medium which contains at least 60% (w/w) monomer. According to the present invention, the first reactor is more preferably a loop reactor.

The second reactor is preferably a first gas phase reactor. Specified lane

- 2 042471 The output gas phase reactor may be any mechanically stirred or fluidized bed reactor or packed bed reactor. Preferably, the first gas phase reactor comprises a mechanically agitated fluidized bed reactor with gas flow rates of at least 0.2 m/s. The first fluidized bed type gas phase reactor may further include a mechanical stirrer to facilitate mixing in the fluidized bed.

The third reactor is preferably a second gas phase reactor. Said second gas phase reactor may be any mechanically agitated or fluidized bed or packed bed reactor. Preferably, the second gas phase reactor comprises a mechanically agitated fluidized bed reactor with gas flow rates of at least 0.2 m/s. The second fluidized bed type gas phase reactor may further include a mechanical stirrer to facilitate mixing in the fluidized bed.

Optional(e) subsequent(e) polymerization reactor or reactors preferably is(are) a gas-phase(e) reactor(s).

The preferred polymerization process is a combined loop and gas phase reactor process such as developed by Borealis and known as the BORSTAR™ technology. Examples of this polymerization process are described in EP 0887379, WO 92/12182, WO 2004/000899, WO 2004/111095, WO 99/24478, WO 99/24479 and WO 00/68315.

When the process according to the present invention generally comprises a pre-polymerization reactor, said pre-polymerization step is carried out prior to polymerization in the first reactor. The prepolymerization step is carried out in a prepolymerization reactor in which propylene is pre(co)polymerized. The pre-polymerization reactor is smaller than the first reactor, second reactor, third reactor and post-polymerization reactor(s) of the present invention, respectively. The reaction volume of the prepolymerization reactor may be, for example, from 0.001 to 10% of the reaction volume of the first reactor, such as a loop reactor. In said prepolymerization reactor, the pre(co)polymerization of propylene is carried out in bulk or slurry to form a propylene (co)polymer.

The operating temperature in the prepolymerization reactor is 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.

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

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

The first reactor of the process according to the present invention is fed with a monomeric feedstock consisting of propylene and optionally one or more comonomers selected from ethylene and C ₄ -C ₁₀ alpha olefins. If the process has a prepolymerization step, the first reactor is also fed with the propylene (co)polymer produced in the prepolymerization reactor. In the first reactor, a fraction of the first propylene polymer is obtained.

The first propylene polymer fraction typically has a comonomer content selected from ethylene and C ₄ -C ₁₀ alpha-olefins in the range of 0.0 to 1.0 wt%, preferably in the range of 0.0 to 0.8 wt% , more preferably in the range from 0.0 to 0.7 wt.% based on the total amount of monomers present in the fraction of the first propylene polymer.

Typically, the first propylene polymer fraction has a melt flow rate (MFR2) in the range of 11 to 60 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. MFR ₂ is determined according to ISO 1133 at 230° C. and under a load of 2.16 kg.

The operating temperature in the first reactor is usually 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.

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.

Hydrogen may be added to the first reactor to control the molecular weight and thus the melt flow rate of the MFR ₂ fraction of the first propylene polymer produced in said first reactor.

Typically, the hydrogen/propylene ratio (I ₂ /C ₃ ) in the first reactor is in the range from 1.5 to 6.0 mol/kmol, preferably in the range from 1.6 to 5.5 mol/kmol, more preferably in range from 1.7 to 5.0 mol/kmol.

- 3 042471

As a rule, the ratio of one or more comonomers (selected from ethylene and C ₄ -C ₁₀ alpha-olefins) to C ₃ in the first reactor is less than 10.0 mol/kmol, preferably in the range from 0.0 to 8.0 mol/kmol, more preferably in the range of 0.0 to 7.5 mol/kmol.

Typically, the reaction mixture of the first reactor is transferred, preferably directly transferred, to the second reactor. By direct transfer is meant a method in which the reaction mixture of the first reactor is sent directly to the next polymerization stage, i.e. to the second reactor. Monomers comprising propylene and one or more comonomers selected from ethylene and C ₄ -C ₁₀ alpha-olefins are fed into the second reactor. In the second reactor, a fraction of the second propylene polymer is obtained.

The fraction of the second propylene polymer usually has a comonomer content selected from ethylene and C ₄ -C ₁₀ alpha-olefins in the range of 0.3 to 2.0 wt.%, preferably in the range of 0.5 to 1.7 wt.% , more preferably in the range from 0.6 to 1.5 wt.%, based on the total amount of monomers present in the fraction of the second propylene polymer.

Typically, the fraction of the second propylene polymer has a melt flow rate (MFR ₂ ) in the range of 11 to 60 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 230°C and under a load of 2.16 kg.

The operating temperature in the second reactor is usually 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.

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.

Hydrogen can be added to the second reactor to control the molecular weight and thus the melt flow rate of the MFR ₂ fraction of the second propylene polymer produced in said second reactor.

Typically, the hydrogen/propylene (H ₂ /C ₃ ) 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 range from 16.0 to 50.0 mol/kmol.

Typically, the ratio of one or more comonomers (selected from ethylene and C ₄ -C ₁₀ alpha olefins) to C3 in the second reactor is in the range from 4.5 to 20.0 mol/kmol, preferably in the range from 5.0 to 18, 0 mol/kmol, more preferably in the range from 5.5 to 17.0 mol/kmol.

As a rule, the reaction mixture of the second reactor is transferred, preferably directly transferred, to the third reactor. By direct transfer is meant a method in which the reaction mixture of the second reactor is sent directly to the next polymerization stage, i.e. to the third reactor. Monomers comprising propylene and one or more comonomers selected from ethylene and C ₄ -C ₁₀ alpha-olefins are fed into the third reactor. In the third reactor, a fraction of the third propylene polymer is obtained.

The fraction of the third propylene polymer usually has a comonomer content selected from ethylene and C ₄ -C ₁₀ alpha-olefins in the range of 1.5 to 5.0 wt.%, preferably in the range of 1.6 to 4.0 wt.% , more preferably in the range from 1.7 to 3.5 wt.%, based on the total amount of monomers present in the fraction of the third propylene polymer.

Typically, the third propylene polymer fraction has a melt flow rate (MFR2) in the range of 12 to 60 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 230°C and under a load of 2.16 kg.

The operating temperature in the third reactor is usually 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.

Typically, the pressure in the third reactor is in the range of 5 to 50 bar, preferably in the range of 15 to 40 bar.

Hydrogen can be added to the third reactor to control the molecular weight and thus the melt flow rate of the MFR ₂ fraction of the third propylene polymer produced in said third reactor.

Typically, the hydrogen/propylene ratio (I ₂ /C ₃ ) in the third reactor is in the range of 15.0 to 80.0 mol/kmol, preferably in the range of 17.0 to 70.0 mol/kmol, more preferably in range from 19.0 to 60.0 mol/kmol.

Typically, the ratio of one or more comonomers (selected from ethylene and C ₄ -C ₁₀ alpha olefins) to C3 in the third reactor is in the range from 45.0 to 200.0 mol/kmol, preferably in the range from 50.0 to 180, 0 mol/kmol, more preferably in the range from 55.0 to 170.0 mol/kmol.

In the method according to the present invention, the propylene polymer obtained in the first reactor, i. the first propylene polymer is usually produced in an amount in the range of 8 to 55% by weight, preferably in an amount in the range of 9 to 52% by weight, more preferably in an amount in the range of 10 to 50% by weight.

- 4 042471

In the method according to the present invention, the propylene polymer obtained in the second reactor, i. the second propylene polymer is usually produced in an amount in the range of 30 to 86% by weight, preferably in an amount in the range of 35 to 80% by weight, more preferably in an amount in the range of 38 to 78% by weight.

In the method according to the present invention, the propylene polymer obtained in the third reactor, i. the third propylene polymer is usually produced in an amount in the range of 6 to 30% by weight, preferably in an amount in the range of 7 to 28% by weight, more preferably in an amount in the range of 8 to 27% by weight. The amounts of the first propylene polymer, the second propylene polymer, and the third propylene polymer are based on the total amount of the first propylene polymer, the second propylene polymer, and the third propylene polymer contained in the third propylene polymer fraction.

In a preferred embodiment, one or more comonomers selected from ethylene and C ₄ -C ₁₀ alpha olefins are introduced into the reactors of the process of the present invention in varying amounts to produce a third propylene polymer fraction having a trimodal comonomer distribution with respect to comonomer content in each of the propylene polymers contained in said fraction of the third propylene polymer, i. e. a first propylene polymer, a second propylene polymer, and a third propylene polymer.

In the process of the present invention, one or more comonomers are selected from ethylene and C ₄ -C ₁₀ alpha olefins, preferably selected from ethylene and C ₄ -C ₈ alpha olefins, more preferably selected from ethylene and C ₄ -C ₆ alpha olefins. , more preferably selected from one or more comonomers including ethylene, even more preferably the comonomer is selected only from ethylene, according to the present invention.

After the polymerization step in the third reactor, the fraction of the third propylene polymer obtained in the third reactor is recovered using conventional methods known to the person skilled in the art. The recovered fraction of the third propylene polymer according to the present invention is usually in the form of particles.

Typically, a polymerization catalyst is present in the process of the present invention. The polymerization catalyst is preferably a Ziegler-Natta catalyst. Typically, a Ziegler-Natta polymerization catalyst contains one or more group 4-6 transition metal (TM) compounds as defined in the IUPAC version 2013, such as titanium, as well as a group 2 metal compound, such as a magnesium compound, and an internal donor ( ID).

The catalyst components may be supported on a particulate support such as, for example, an inorganic oxide such as, for example, silica or alumina. Alternatively, a magnesium halide may form a solid support. It is also possible that the catalyst components are not applied to the outer support and the catalyst is produced by an emulsion curing method or by a precipitation method, as is well known to the person skilled in the art of catalyst production.

Preferably, a particular type of Ziegler-Natta catalyst is present in the process of the present invention. It is important that in said particular type of Ziegler-Natta catalyst, the internal donor is a non-phthalic compound. It is preferable not to use phthalic compounds during the entire process of preparing a particular type of Ziegler-Natta catalyst, so that the final Ziegler-Natta catalyst of a particular type does not contain any phthalic compounds. Thus, a specific type of Ziegler-Natta catalyst does not contain phthalic compounds. Therefore, the fraction of the third propylene polymer obtained in the third reactor of the process according to the present invention does not contain phthalic compounds.

Typically, a particular type of Ziegler-Natta catalyst contains an internal donor (ID) that is selected from compounds other than phthalic compounds, thus a particular type of Ziegler-Natta catalyst is completely free of phthalic compounds. In addition, a specific type of Ziegler-Natta catalyst may be a solid catalyst, which preferably does not contain any external support material such as silica or MgCl ₂ , and thus the solid catalyst is self-supported. .

A solid catalyst is prepared using the following general procedure:

a) providing a solution a1) of at least an alkoxy compound of a group 2 metal (Ax) which is the reaction product of a group 2 metal compound and an alcohol (A) containing in addition to the hydroxyl moiety at least one ether moiety, optionally in an organic liquid reaction medium , or a ₂ ) at least an alkoxy compound of a group 2 metal (Ax') which is the reaction product of a group 2 metal compound and an alcoholic mixture of an alcohol (A) and a monohydric alcohol (B) of the formula ROH, optionally in an organic liquid reaction medium, or a ₃ ) mixtures of a group 2 metal alkoxy compound (Ax) and a group 2 metal alkoxy compound (Bx) which is the reaction product of a group 2 metal compound and a monohydric alcohol (B), optional

- 5 042471 but in an organic liquid reaction medium, or a ₄ ) group 2 metal alkoxy compounds of formula M(OR1) _n (OR ₂ ) _m X _2-n- m or mixtures of group 2 alkoxides M(OR1) _n 'X _2-n ' and M(OR ₂ ) _m X ₂ _ _mS where M is a Group 2 metal, X is halogen, R1 and R2 are various alkyl groups containing from 2 to 16 carbon atoms, and 0<n<2.0 <m<2 and n+m+(2-nm)=2 provided that n and m are not simultaneously equal to 0, 0<n'<2 and 0<m'<2; And

b) adding said solution from step a) to at least one group 4-6 transition metal compound; And

c) obtaining solid catalyst component particles, and adding a non-phthalic internal electron donor (ID) at least one step before step c).

The internal donor (ID) or its precursor is preferably added to the solution from step a) or to the transition metal compound before adding the solution from step a).

According to the procedure described above, a solid catalyst can be obtained by a precipitation method or by an emulsion curing method, depending on the physical conditions, especially the temperature used in steps b) and c). An emulsion is also referred to as a two-phase liquid-liquid system. In both methods (precipitation or emulsion curing), the chemical composition of the catalyst is the same.

In the precipitation method, the combination of the solution from step a) with at least one transition metal compound is carried out in step b) and the entire reaction mixture is kept at at least 50°C, more preferably in the temperature range from 55 to 110°C, more preferably at range from 70 to 100°C to ensure complete deposition of the catalyst component in the form of particles of the solid catalyst component (stage c)).

In the emulsion curing process in step b), the solution from step a) is usually added to at least one transition metal compound at a lower temperature, for example -10°C to less than 50°C, preferably -5 to 30°C. During mixing of the emulsion, the temperature is usually maintained at -10°C to less than 40°C, preferably from -5 to 30°C. Drops of the dispersed phase of the emulsion form an active catalytic composition. The curing (step c)) of the drops is carried out by heating the emulsion to a temperature of 70 to 150°C, preferably 80 to 110°C. In the present invention, the catalyst obtained by the emulsion curing method is preferably used.

In step a) preferably a solution a ₂ ) or a ₃ ) is used, i.e. a solution of (Ax') or a solution of a mixture of (Ax) and (Bx).

Preferably the Group 2 metal is magnesium. Magnesium alkoxy compounds (Ax), (Ax'), (Bx) can be prepared in situ in the first step of the catalyst preparation process, step a), by reacting a magnesium compound with an alcohol(s) as described above. Another option is to obtain these magnesium alkoxy compounds separately, or they can even be purchased in the form of already prepared magnesium alkoxy compounds and used as such in the process for preparing a catalyst according to the present invention.

Illustrative examples of alcohols (A) are glycol monoethers. Preferred alcohols (A) are C ₂ -C ₄ glycol monoethers in which the ether moieties contain 2 to 18 carbon atoms, preferably 4 to 12 carbon atoms. Preferred examples are 2-(2-ethylhexyloxy)ethanol, 2-butyloxyethanol, 2-hexyloxyethanol and 1,3-propylene glycol monobutyl ether, 3-butoxy-2-propanol, while 2-(2-ethylhexyloxy)ethanol, monobutyl 1,3-propylene glycol ether and 3-butoxy-2-propanol are especially preferred.

An exemplary monohydric alcohol (B) is represented by the structural formula ROH, where R is a straight or branched C ₂ -C ₁₆ alkyl radical, preferably a C ₄ -C ₁₀ alkyl radical, more preferably a C ₆ -C ₈ alkyl radical. The most preferred monohydric alcohol is 2-ethyl-1-hexanol or octanol.

Preferably, a mixture of Mg alkoxy compounds (Ax) and (Bx) or a mixture of alcohols (A) and (B), respectively, is used and is used in a molar ratio of Bx:Ax or B:A from 10:1 to 1:10, more preferably from 6 :1 to 1:6, more preferably 5:1 to 1:3, most preferably 5:1 to 3:1.

The magnesium alkoxy compound may be a reaction product between the alcohol(s) as defined above and a magnesium compound selected from dialkyl magnesium, alkyl magnesium alkoxide, magnesium dialkoxide, alkoxy magnesium halide, and alkyl magnesium halide. In addition, magnesium dialkoxide, magnesium diaryloxide, magnesium aryloxyhalide, magnesium aryloxide and magnesium alkylaryloxide can be used. The alkyl groups in the magnesium compound may be the same or different C 1 -C ₂₀ alkyl groups, preferably C ₂ -C ₁₀ alkyl groups. When used, typical magnesium alkyl alkoxy compounds are ethyl magnesium butoxide, butyl magnesium pentoxide, octyl magnesium butoxide and octyl magnesium octoxide. Preferably, dialkyl compounds are used.

- 6 042471 The most preferred magnesium dialkyl compounds are butyl octyl magnesium or butyl ethyl magnesium.

It is also possible that the magnesium compound, in addition to the alcohol (A) and alcohol (B), reacts with a polyhydric alcohol (C) of the formula R(OH) _m to form said magnesium alkoxide. When used, preferred polyhydric alcohols are those in which R is a C2-C10 linear, cyclic or branched hydrocarbon residue and m is an integer from 2 to 6.

Thus, the magnesium alkoxy compounds of step a) are selected from the group consisting of magnesium dialkoxides, magnesium diaryloxy compounds, alkyloxy magnesium halides, aryloxy magnesium halides, alkyl magnesium alkoxides, aryl magnesium alkoxides and alkyl magnesium aryl oxides, or a mixture of magnesium dihalide and magnesium dialkoxide.

The solvent to be used to prepare the catalyst of the present invention may be selected from linear, branched or cyclic aromatic and aliphatic hydrocarbons containing from 5 to 20 carbon atoms, more preferably from 5 to 12 carbon atoms, or mixtures thereof. Suitable solvents include benzene, toluene, cumene, xylene, pentane, hexane, heptane, octane and nonane. Hexanes and pentanes are particularly preferred.

The reaction to obtain a magnesium alkoxy compound can be carried out at a temperature of 40 to 70°C. One skilled in the art will know how to select the most appropriate temperature depending on the Mg compound and alcohol(s) used.

Groups 4-6 transition metal (TM) compound, as defined in IUPAC version 2013, is preferably a titanium compound, most preferably a titanium halide such as TiCl4.

The non-phthalic internal donor (ID) used to prepare the specific type of Ziegler-Natta catalyst used in the present invention is preferably selected from mono- and diesters of non-phthalic mono- and dibasic carboxylic acids, 1,3-diesters, derivatives and mixtures thereof. A particularly preferred donor is a diester of monounsaturated non-phthalic dicarboxylic acids, in particular an ester belonging to the group consisting of malonates, maleates, succinates, citraconates, glutarates, cyclohexene-1,2-dicarboxylates and benzoates, their derivatives and/or mixtures. Preferred examples are, for example, substituted maleates and citraconates, most preferably citraconates.

Hereinafter, the term derivative includes substituted compounds.

In an emulsion curing process, a two-phase liquid-liquid system can be obtained by simply mixing and optionally adding (then) solvent(s) and/or additives such as a turbulence minimizing agent (TMA) and/or an emulsifier and/or a stabilizer emulsions, such as a surfactant, which are applied in a manner known in the art. These solvents and/or additives are used to facilitate the formation of the emulsion and/or its stabilization. Preferably the surfactants are acrylic or methacrylic polymers. Particularly preferred are linear C ₁₂ -C ₂₀ (meth)acrylates such as, for example, poly(hexadecyl)methacrylate and poly(octadecyl)methacrylate and mixtures thereof. When used, a turbulence minimizing agent (TMA) is preferably selected from polymers of α-olefin monomers containing from 6 to 20 carbon atoms, such as polyoctene, polynonene, polydecene, polyundecene or polydodecene, or mixtures thereof. Most preferred is polydecene.

The particulate solid product obtained by the precipitation or emulsion curing process may be washed at least once, preferably at least twice, most preferably at least three times. Washing can be carried out using an aromatic and/or aliphatic hydrocarbon, preferably toluene, heptane or pentane. Washing with TiCl4 is also possible, optionally in combination with an aromatic and/or aliphatic hydrocarbon. Wash liquids may also contain donors and/or Group 13 compounds such as trialkylaluminums, halogenated alkylaluminum compounds, or alkoxyaluminum compounds. Aluminum compounds can also be added during catalyst preparation. The catalyst may be further dried, for example by evaporation or nitrogen purge, or it may be suspended in an oily liquid without any drying step.

The final type of Ziegler-Natta catalyst produced is desirably in the form of particles having in general an average particle size in the range of 5 to 200 µm, preferably 10 to 100 µm. The particles are typically compact with low porosity and typically have a surface area of less than 20 g/m ² , more preferably less than 10 g/m ² . Typically, the amount of Ti present in the catalyst is in the range of 1 to 6 wt.%, the amount of Mg is in the range of 10 to 20 wt.%, and the amount of internal donor present in the catalyst is in the range of 10 to 40 wt. % catalyst composition. A detailed description of the preparation of the catalysts used in the present invention is given in WO 2012/007430, EP 2610271 and EP 2610272,

- 7 042471 which are incorporated into the present application by reference.

In the polymerization process according to the present invention, an external donor (ED) is preferably present as an additional component. Suitable external donors (ED) include certain silanes, ethers, esters, amines, ketones, heterocyclic compounds, and mixtures thereof. It is particularly preferred to use silanes. Most preferably, silanes of general formula (I) are used.

R ^a pR ^b qSi(OR ^c )(4.pq) (I) where R ^a , R ^b and R ^c denote a hydrocarbon radical, in particular an alkyl or cycloalkyl group, and 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 may be selected independently of each other and may be the same or may be different. Specific examples of silanes according to formula (I) are (tert-butyl) ₂ Si(OCH ₃ ) ₂ , (cyclohexyl)(methyl)81(OCH ₃ ) ₂ , (phenyl) ₂ Si(OCH ₃ ) ₂ and (cyclopentyl) ₂ Si(OCH ₃ ) ₂ . Another most preferred silane corresponds to the general formula (II)

where R ³ and R ⁴ may be the same or may be different and represent a linear, branched or cyclic hydrocarbon group containing from 1 to 12 carbon atoms.

It is especially preferred that R ³ and R ⁴ are independently selected from the group consisting of methyl, ethyl, n-propyl, n-butyl, octyl, decanyl, isopropyl, isobutyl, isopentyl, t-butyl, mpem-amyl, neopentyl, cyclopentyl , cyclohexyl, methylcyclopentyl and cycloheptyl. Most preferably, ethyl is used.

Typically, in addition to a Ziegler-Natta catalyst or a particular type of Ziegler-Natta catalyst and an optional external donor (ED), a co-catalyst (Co) may be present in the polymerization process of the present invention. The cocatalyst is preferably a compound of an element of group 13 of the periodic table (IUPAC, version 2013), such as, for example, an aluminum compound, such as an organoaluminum compound or an aluminum halide. An example of a suitable organoaluminum compound is alkylaluminum or alkylaluminum halide. Accordingly, in one particular embodiment, the cocatalyst (Co) is a trialkylaluminum such as triethylaluminum (TEAL), dialkylaluminum chloride or alkylaluminum dichloride, or mixtures thereof. In one particular embodiment, the cocatalyst (Co) is triethylaluminum (TEAL).

Typically, the molar ratio between cocatalyst (Co) and external donor (ED) [Co/ED] and/or the mole ratio between cocatalyst (Co) and transition metal (TM) [Co/TM] is carefully selected for each process. The mole ratio between the cocatalyst (Co) and the external donor (ED), [Co/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 from 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 specified values of the ranges are included in them.

The mole ratio between cocatalyst (Co) and transition metal (TM), [Co/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 from 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 specified values of the ranges are included in them.

According to the present invention, the fraction of the third propylene polymer recovered from the polymerization process is extruded in the presence of at least one alpha-nucleating agent to obtain a polypropylene composition according to the present invention.

The extruder on which the extrusion step is carried out may be any extruder known in the art. Thus, the extruder may 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. A particularly preferred extruder is a co-rotating twin screw extruder.

The extruder typically has a loading zone, a melting zone, a mixing zone and optionally a molding zone.

The extruder typically has a length to diameter ratio, L/D, up to 60:1, preferably up to 40:1.

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The extruder may also have one or more feed openings for introducing additional components into the extruder, such as, for example, additives. The location of these additional feed openings depends on the type of material added through the opening.

Examples of additives include, but are not limited to, stabilizers such as antioxidants (e.g., hindered phenols, phosphites/phosphonites, sulfur containing antioxidants, alkyl radical scavengers, aromatic amines, hindered amine stabilizers, or mixtures thereof), metal deactivators (e.g., Irganox® MD 1024) or UV stabilizers (eg hindered amine light stabilizers). Other typical additives are modifiers such as antistatic or anti-flocculation agents (eg ethoxylated amines and glycerol amides or esters), acid scavengers (eg Ca stearate), blowing agents, tackifiers (eg polyisobutene), lubricants and resins. (for example, ionomer waxes, waxes based on polyethylene and ethylene copolymers, Fischer-Tropsch waxes, montan waxes, fluorine-based compounds or paraffin waxes), as well as anti-friction and anti-adhesion agents (for example, erucamide, oleamide, talc, natural silica and synthetic silica or zeolites) and mixtures thereof.

Generally, the total amount of additives added to the extruder in the process of the present invention is not more than 5.0 wt%, preferably not more than 2.0 wt%, more preferably not more than 1.5 wt%. The amount of additives is based on the total amount of polypropylene composition introduced into the extruder.

In the process of the present invention, the third propylene polymer fraction is extruded at a temperature which is higher than the melting point of the third propylene polymer fraction but less than the decomposition temperature of the third propylene polymer fraction. Suitably, the third propylene polymer fraction is extruded at a temperature at least 30°C above the melting point of the third propylene polymer fraction, preferably the third propylene polymer fraction is extruded at a temperature at least 40°C above the melting point of the third propylene polymer fraction, more preferably, the third propylene polymer fraction is extruded at a temperature at least 50° C. higher than the melting point of the third propylene polymer fraction, but lower than the decomposition temperature of the third propylene polymer fraction, i. less than 300°С.

In the method according to the present invention, a fraction of the third propylene polymer is extruded in the presence of an amount of at least one alpha-nucleating agent in the range from 0.01 to 1.0 wt.%, preferably in the range from 0.03 to 0.9 wt.%, more preferably in the range from 0.05 to 0.8 wt.%. The amount of at least one alpha-nucleating agent is based on the total amount of the polypropylene composition according to the present invention. The α-nucleating agent is typically selected from the group consisting of (i) salts of monobasic carboxylic acids and polybasic carboxylic acids, for example sodium benzoate or aluminum t-butyl benzoate;

(ii) dibenzylidene sorbitol (for example, 1,3:2,4-dibenzylidene sorbitol) and C1-C8 alkyl-substituted derivatives of dibenzylidene sorbitol, such as methyldibenzylidene sorbitol, ethyldibenzylidene sorbitol, or dimethyldibenzylidene sorbitol (for example, 1,3:2,4-di(methylbenzylidene)sorbitol), or substituted nonitic derivatives such as 1,2,3-trideoxy-4,6:5,7-bis-O-[(4-propylphenyl)methylene]nonite;

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

(iv) a vinyl cycloalkane polymer and a vinyl alkane polymer; and (v) mixtures thereof.

Preferably the α-nucleating agent is dibenzylidene sorbitol (e.g. 1,3:2,4-dibenzylidene sorbitol) or a C1-C8 alkyl substituted derivative of dibenzylidene sorbitol such as methyldibenzylidene sorbitol, ethyldibenzylidene sorbitol or dimethyldibenzylidene sorbitol (e.g. 1,3:2,4-di(methylbenzylidene )sorbitol) or a substituted nonitic derivative such as 1,2,3-trideoxy4,6:5,7-bis-O-[(4-propylphenyl)methylene]nonite.

At least one α-nucleating agent is usually fed into the extruder through the feed zone. However, the at least one α-nucleating agent may be fed into the extruder through one or more feed ports provided in the extruder, such as through a side feed port.

At the end of the extruder, a melt of the polypropylene composition is obtained. Then the melt of the polypropylene composition according to the present invention can be passed through the die in the optional molding zone of the extruder. When the melt of the polypropylene composition according to the present invention is passed through the die, it is usually further cooled and granulated.

The shaping zone usually includes the head, which is usually a thick metal disc with several holes. The holes are parallel to the axis of the screw.

The granulator is usually a strand granulator or an underwater granulator.

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The present invention also provides a polypropylene composition obtainable, preferably obtained, by the method of the present invention.

The polypropylene composition obtained, preferably obtained, by the process of the present invention generally contains one or more comonomers selected from ethylene and C|-C| ₀ alpha olefins, preferably selected from ethylene and C ₄ -C8 alpha olefins, more preferably selected from ethylene and C ₄ -C ₆ alpha olefins, even more preferably selected from one or more comonomers including ethylene, even more preferably comonomer selected from ethylene only.

The polypropylene composition obtained, preferably obtained, by the method of the present invention has a comonomer content in the range of 1.5 to 5.0 wt.%, preferably in the range of 1.6 to 4.0 wt.%, more preferably in range from 1.7 to 3.5 wt.%. The comonomer content is based on the total amount of monomers present in the polypropylene composition.

Generally, the polypropylene composition obtained, preferably obtained, by the method of the present invention has a melt flow rate (MFR2) in the range of 12 to 60 g/10 min, preferably in the range of 15 to 40 g/10 min, more preferably in the range from 17 to 35 g/10 min. MFR2 is determined according to ISO 1133 at 230°C and under a load of 2.16 kg.

Generally, the polypropylene composition obtained, preferably obtained, by the process 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 1 mm thick injection molded plates manufactured as described in EN ISO 1873-2.

As a rule, the polypropylene composition obtained, preferably obtained, using the method according to the present invention, has a melting point of >152°C, preferably in the range from 153 to 163°C, more preferably in the range from 154 to 162°C. The melting point (Tm) is measured by DSC according to ISO 11357/3.

As a rule, the polypropylene composition obtained, preferably obtained, using the method according to the present invention, has a crystallization temperature of >120°C, preferably in the range from 122 to 132°C, more preferably in the range from 123 to 130°C. The crystallization temperature (TC) is measured by DSC in accordance with ISO 11357/3.

As a rule, the polypropylene composition obtained, preferably obtained, using the method according to the present invention, has a xylene-soluble fraction (XCS) content in the range from 5.5 to 18.0 wt.%, preferably in the range from 6.0 up to 16.0 wt.%, more preferably in the range from 6.2 to 15.0 wt.%. The xylene soluble fraction is determined according to ISO 16152 at 25°C.

Generally, the polypropylene composition obtained, preferably obtained, by the method of the present invention has a tensile modulus of >950 MPa, more preferably in the range of 951 to 1600 MPa, more preferably in the range of 1000 to 1600 MPa, even more preferably in the range from 1050 to 1550 MPa. Tensile modulus is measured in accordance with ISO 527-1:2012/ISO 527-2:2012 at 23° C. on injection molded test specimens.

As a rule, the polypropylene composition obtained, preferably obtained, using the method according to the present invention, has a notched Charley impact strength of >4.8 kJ/m ² , preferably in the range from 4.9 to 20.0 kJ/m ² , more preferably in the range of 5.0 to 15.0 kJ/m ² , more preferably in the range of 5.0 to 13.0 kJ/m ² , more preferably in the range of 7.0 to 13 kJ/m ² . Charlie 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.

The present invention also provides an article containing a polypropylene composition obtained, preferably obtained, using the method according to the present invention. Suitable articles are films, such as, for example, cast films, and articles made by injection molding. A preferred product is a closure cap, threaded cap or closure system for food or liquid packaging.

Finally, the present invention relates to the use of a polypropylene composition obtainable, preferably obtained, by means of the process of the present invention for the manufacture of a solution-cast film or injection molded article, preferably a closure cap, threaded cap or closure system for food packaging. or liquids. A fluid is usually defined as a substance that permanently deforms (flows) under the influence of an applied shear stress.

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Examples

I. Methods of measurement.

a) Melt flow rate.

The melt flow rate (MFR) was determined according to ISO 1133 and reported in g/10 min. MFR is an indicator of the flowability and hence the processability of a polymer. The higher the melt flow rate, the lower the viscosity of the polymer. The MFR2 of polypropylene was determined at 230° C. and under a load of 2.16 kg.

b) DSC analysis.

The melting point and crystallization temperature were measured using a differential scanning calorimetry (DSC) device TA Instrument Q2000 according to ISO 11357/3 on samples weighing 5-10 mg under a nitrogen atmosphere of 50 ml/min. The crystallization and melting temperatures were obtained in a heating/cooling/heating cycle at a scan rate of 10°C/min in the range from 30 to 225°C. The peaks of the endothermic and exothermic curves at the stage of cooling and the second stage of heating, respectively, were taken as the crystallization and melting temperatures.

c) The content of the xylene-soluble fraction (XCS, wt.%).

The xylene-soluble polymer content was measured according to ISO 16152; 5th edition; 2005-07-01 at 25°C.

d) Tensile modulus.

Tensile modulus was measured according to ISO 527-1:2012/ISO527-2:2012 at 23°C and cross head speed=50 mm/min using injection molded test specimens as described in EN ISO 1873-2 (dog bone shape, 4 mm thick).

e) Notched Charpy impact strength.

Charpy notched impact strength was determined according to ISO 179/1eA at 23° C. on injection molded test specimens as described in EN ISO 1873-2 (80x10x4 mm).

f) Turbidity.

Haze was measured according to ASTM D1003 on injection molded plates 1 mm thick and 60x60 mm ² in area, manufactured as described in EN ISO 1873-2.

g) Comonomer content.

Determination of the content of ethylene in copolymers of propylene and ethylene by IR spectroscopy.

Quantitative infrared (IR) spectroscopy was used to quantify the ethylene content of ethylene-propylene copolymers by calibrating against a primary standard.

Calibration was simplified by using a set of proprietary non-commercial calibration standards with known ethylene contents determined by quantitative ¹³ C nuclear magnetic resonance (NMR) spectroscopy in solution. The calibration procedure was carried out in the usual way, well described in the literature. The calibration set consisted of 38 calibration standards with an ethylene content in the range of 0.2-75.0 wt.%, made on a laboratory or industrial scale under various conditions. The calibration set was chosen to reflect the typical diversity of copolymers found by the final quantitative IR spectroscopy method.

Quantitative IR spectra were recorded in the solid state using a Bruker Vertex 70 FTIR spectrometer. The spectra were recorded on 300 µm thick 25x25 mm square films made by compression molding at 180-210°C and 4-6 MPa. For samples with a very high content of ethylene (>50 mol.%) used films with a thickness of 100 μm. Standard FT-IR transmission spectroscopy was used using a spectral range of 5000-500 cm ^-1 , an aperture of 6 mm, a spectral resolution of 2 cm ^-1 , 16 background scans, 16 spectrum scans, an interferogram zero fill factor of 64, and a three-term apodization function Blackman Harris.

Quantitative analysis was performed using the total area of vibrational strains of CH2 at 730 and 720 cm ^-1 (Aq), corresponding to (CH2)>2 structural units (integration method G, limits 762 and 694 cm ^-1 ). The quantitative band was normalized to the area of the CH band at 4323 cm ^-1 (AR) corresponding to the CH structural units (integration method G, limits 4650, 4007 cm ^-1 ). The ethylene content was then predicted in terms of mass percent based on normalized absorbance (Aq/Ar) using a quadratic calibration curve. A calibration curve was previously constructed by OLS regression of the normalized absorbances and primary comonomer contents measured with the calibration kit.

Determination of ethylene content in propylene-ethylene copolymers for calibration using ¹³ C NMR spectroscopy.

Quantitative ¹³ C{1H} NMR spectra were recorded in solution using a Bruker Avance III 400 NMR spectrometer operating at 400.15 and 100.62 MHz for 1H and ¹³ C, respectively. All spectra

- 11 042471 was recorded using a ¹³ ° C. optimized 10 mm extended temperature probe head at 125° C. using nitrogen gas for all pneumatics. Approximately 200 mg of the material was dissolved in 3 ml of 1,2-tetrachloroethane-d ₂ (TCE-d ₂ ) together with chromium (III) acetylacetonate (Cr(acac) ₃ ) to give a 65 mM solution of the relaxation agent in a solvent (Singh, G. , Kothari, A., Gupta, V., Polymer Testing 28 5 (2009), 475). To ensure homogeneity of the solution after the initial sample preparation in the oven, the NMR tube was additionally heated in a rotating drying chamber for at least 1 hour. After being inserted into the magnet, the tube was rotated at a frequency of 10 Hz. This setup was chosen primarily to provide the high resolution and quantity needed to accurately quantify the ethylene content. Standard single-pulse excitation was applied without NOE using an optimized tilt angle, recovery latency of 1 s, 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) transitions per spectrum were obtained. Quantitative ¹³ C{ ¹ H} NMR spectra were processed, integrated and the corresponding quantitative properties were determined from the integrals. All chemical shifts were indirectly assigned to the central methylene group of the ethylene block (EEE) at 30.00 ppm. (ppm) using solvent chemical shift. This approach made it possible to carry out a comparison even in the absence of the indicated structural link. Characteristic signals corresponding to ethylene incorporation were observed (Cheng, HN, Macromolecules, 17 (1984), 1950) and the comonomer fraction was calculated as the proportion of ethylene in the polymer relative to all monomers in the polymer by the formula

W=(E/(P+E))

The proportion of comonomer was quantified using the method proposed by Wang (Wang) et al. (Wang, WJ., Zhu, S., Macromolecules, 33 (2000), 1157) by integrating multiple signals over the entire spectral region in ¹³ C{1H} spectra. This method was chosen because of its reliability and the ability to take into account the presence of regio-defects, if necessary. The integral regions were slightly adjusted to improve applicability over the entire range of detectable comonomers. For very low ethylene systems where only isolated ethylene was observed in the PPEPP sequences, the method proposed by Wang et al. was modified to reduce the effect of integrating regions that were no longer present. This approach made it possible to reduce the overestimation of the ethylene content for such systems and was provided by reducing the number of sites used to determine the absolute content of ethylene to

Е=0.5(Sββ+Sβγ+Sβδ+0.5(Sαβ+Sαγ))

Due to the use of the specified set of sections, the corresponding integral equation took the form

E=0.5(Ih+Ig+0.5(Ic+Id)) using the same notation as used in Wang et al. (Wang, W-J., Zhu, S., Macromolecules 33 (2000), 1157). The equations used for the absolute content of propylene were not modified. The mole percentage of comonomer incorporation was calculated from the mole fraction

E [mol.%] \u003d 100 * £B

The weight percentage of comonomer incorporation was calculated based on the mole fraction E[wt%]=100*(fE*28.06)/((fE*28.06)+((1-fE)*42.08))

II. Examples according to the present invention and comparative examples.

a) Preparation of a catalyst.

To prepare the catalyst, 3.4 L of 2-ethylhexanol and 810 ml of propylene glycol monobutyl ether (4/1 mole ratio) were added to a 20.0 L reactor. Then, 7.8 liters of a 20.0% solution of BEM (butylethylmagnesium) in toluene, provided by Crompton GmbH, was slowly added to the well stirred alcohol mixture. During the addition, the temperature was maintained at 10.0°C. After the addition, the temperature of the reaction mixture was raised to 60.0° C. and stirring was continued at the same temperature for 30 minutes. Finally, after cooling to room temperature, the resulting Mg alkoxide was transferred to a storage vessel.

21.2 g of the Mg alkoxide prepared above was mixed with 4.0 ml of bis(2-ethylhexyl)citraconate for 5 minutes. After mixing, the resulting Mg complex was immediately used to prepare the catalyst component.

19.5 ml of titanium tetrachloride were placed in a 300 ml reactor equipped with a mechanical stirrer at 25.0°C. The stirring speed was adjusted to 170 rpm. 26.0 g of the Mg complex prepared above was added over 30 minutes while maintaining the temperature at 25.0°C. 3.0 ml of Viscoplex® 1-254 and 1.0 ml of a 2 mg solution of Necadd 447™ in toluene were added. Then 24.0 ml of heptane was added to form an emulsion. Stirring was continued for 30 minutes at 25.0°C, after which the reactor temperature was raised to 90.0°C over 30 minutes. The reaction mixture was stirred for an additional 30 min at

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90.0°C. Then the stirring was stopped and the reaction mixture was allowed to stand for 15 min at 90.0°C. The solid material was washed 5 times: washings were carried out at 80.0° C. with stirring for 30 minutes at 170 rpm. After cessation of stirring, the reaction mixture was allowed to stand for 20-30 min, and then subjected to siphoning.

Wash 1: Wash was performed with a mixture of 100 ml of toluene and 1 ml of donor.

Wash 2: Wash was performed with a mixture of 30 ml TiCl ₄ and 1 ml donor.

Wash 3: Wash was carried out with 100 ml of toluene.

Wash 4: Wash was performed with 60 ml of heptane.

Wash 5: Wash with 60 ml heptane with stirring for 10 minutes.

Then the stirring was stopped and the reaction mixture was allowed to stand for 10 min while lowering the temperature to 70°C, followed by siphoning, and then purged with N ₂ for 20 min to obtain an air-sensitive powder.

b) Examples according to the present invention (IE1 and IE2).

Fractions of the third propylene polymers related to the examples according to the present invention (IE) were obtained in a pilot plant with a prepolymerization reactor, one slurry loop reactor and two gas phase reactors. The solid catalyst component described above, together with triethylaluminum (TEAL) as a cocatalyst and dicyclopentyldimethoxysilane (D-donor) as an external donor, was used in the process of the present invention.

The conditions of the polymerization process and the properties of the fraction of the propylene polymer are described in table. 1.

The polypropylene compositions of the present invention were obtained by extruding an appropriate fraction of the third propylene polymer with a nucleating agent in a co-rotating twin screw extruder of the Coperion ZSK 40 type (screw diameter 40 mm, L/D ratio 38). The temperatures in the extruder were in the range of 190-230°C. In each of the examples according to the present invention, 0.05 wt.% Irganox 1010 (pentaerythrityltetrakis(3-(3',5'-di-tert-butyl-4-hydroxyphenyl))propionate, CAS No. 6683-19 -8, commercially available from BASF AG, Germany), 0.05 wt% Irgafos 168 (tris(2,4-di-tert-butylphenyl)phosphite, CAS No. 31570-04-4, commercially available from BASF AG, Germany ), 0.10 wt.% calcium stearate (CAS no. 1592-23-0, commercially available under the trade name Ceasit FI from Baerlocher GmbH, Germany) and 0.06 wt.% glycerol monostearate (CAS no. 97593-29-8, commercially available in 90% purity under the trade name Grindsted PS 426 manufactured by Danisco A/S, Denmark).

After the extrusion step and after curing the filaments in a water bath, the obtained polypropylene composition was granulated in a strand granulator.

The properties of the polypropylene composition are described in table. 2.

c) Comparison examples (CE1 and CE2).

CE-1 is a random copolymer of propylene and C ₂ with an MFR2 value of 13.0 g/10 min, obtained in a one-pot process and distributed by Borealis under the trade name RE420MO.

CE-2 is a random copolymer of propylene and C2 with an MFR2 value of 20.0 g/10 min produced in a one pot process and distributed by Borealis under the trade name RF365MO.

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Table 1

Conditions of the polymerization process and properties of propylene polymer fractions

1 IE1 IE2 Pre-polymerization reactor Temperature [°C] thirty thirty Catalyst supply [g/h] 2.5 2.6 D-donor [g/t propylene] 41 41 TEAL/propylene [g/t propylene] 170 170 Al/D donor [Co/ED] [mol/mol] 8.3 8.2 Al/Ti [Co/TM] [mol/mol] 217 211 Time of stay [h] 0.3 oh, s Loop reactor (fraction of the first propylene polymer Temperature [°C] 70 70 Pressure [kPa] 5270 5270 Time of stay [h] 0.4 0.4 breakdown [%] 47 36 H2/C3 ratio [mol/kmol] 2.4 2.3 C2/C3 ratio [mol/kmol] 3.6 3.6 MFR2 [g/10 min] 24.8 21.9 Content C2 [wt%] 0.5 0.4 First gas phase reactor (second propylene polymer fraction) Temperature [°C] 80 80 Pressure [kPa] 2400 2400 Time of stay [h] 1.4 1.4 breakdown [%] 38 48 H2/C3 ratio [mol/kmol] 28.7 27.2 C2/C3 ratio [mol/kmol] 9.2 9.1 MFR2 [g/10 min] 22.4 19.0 Content C2 [wt%] 0.98 0.93 Second gas phase reactor (third propylene polymer fraction) Temperature [°C] 80 80 Pressure [kPa] 2350 2350 Time of stay [h] 0.9 0.9 breakdown [%] 15 16 H2/C3 ratio [mol/kmol] 36.9 45.4 C2/C3 ratio [mol/kmol] 69.3 71.2 MFR2 [g/10 min] 19.0 18.4 Content C2 [wt%] 2.6 h, o

* The breakdown refers to the amount of propylene polymer produced in each particular reactor.

table 2

Extrusion process conditions and properties of the polypropylene composition

IEI IE2 CE1 CE2 Nucleating agent (Millad 3988®) [wt%] 0.17 0.17 0.0 0.0 Composition Properties* MFR2 [g/10 min] 19.0 18.0 13 20 Content C2 [wt%] 2.6 2.9 3.4 3.4 XCS [wt%] 6.9 8.6 5.8 6.8 Tensile modulus [MPa] 1305 1240 921 1138 Notched specimen impact strength Charlie [kJ / m ² ] 5.5 7.22 5.3 4.5 Haze (1 mm) [%] 17 15 23 20 Tt [°C] 160 159 150 151 Ts [°C] 128 128 120 120

* Measured on pellets obtained after the extrusion process.

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Claims (18)

From Table. 2, it can be concluded that the polypropylene compositions (examples according to the present invention) show an improved balanced combination of high flow, high stiffness and impact resistance and high level of optical properties (low haze value) compared to the comparative examples. CLAIM 1. A method for producing a polypropylene composition by sequential polymerization, including the steps a) polymerization in the first reactor of monomers comprising propylene and optionally one or more comonomers selected from ethylene and C ₄ -C ₁₀ alpha-olefins, obtaining a fraction of the first propylene polymer with a comonomer content in the range from 0.0 to 1.0 wt .%; b) polymerizing in a second reactor monomers comprising propylene and one or more comonomers selected from ethylene and C ₄ -C ₁₀ alpha-olefins in the presence of a first propylene polymer fraction to obtain a second propylene polymer fraction with a comonomer content ranging from 0.3 up to 2.0 wt.%; c) polymerizing in a third reactor monomers comprising propylene and one or more comonomers selected from ethylene and C ₄ -C ₁₀ alpha-olefins in the presence of a second propylene polymer fraction to obtain a third propylene polymer fraction with a comonomer content ranging from 1.5 up to 5.0 wt.%; d) extruding a third propylene polymer fraction in the presence of at least one alpha-nucleating agent, wherein the polypropylene composition has an MFR ₂ value in the range of 12.0 to 60.0 g/10 min, measured according to ISO 1133 at 230°C under load of 2.16 kg. 2. Method according to claim 1, characterized in that the first reactor is a slurry reactor. 3. Process according to claim 1 or 2, characterized in that the second reactor is a gas phase reactor. 4. Process according to any one of the preceding claims, characterized in that the third reactor is a gas phase reactor. 5. Process according to any one of the preceding claims, characterized in that said sequential polymerization is carried out in the presence of a Ziegler-Natta catalyst, preferably a Ziegler-Natta catalyst which does not contain phthalic compounds. 6. The method according to claim 5, characterized in that the Ziegler-Natta catalyst is a Ziegler-Natta catalyst with a transition metal of groups 4-6 of the periodic table, containing an internal donor, optionally a cocatalyst and optionally an external donor, and the internal donor is a non-phthalic internal donor. 7. The method according to claim 6, characterized in that the non-phthalic internal donor is selected from the diesters of non-phthalic dibasic carboxylic acids, and the diester belongs to the group including malonates, maleates, succinates, citraconates, glutarates, cyclohexene-1,2-dicarboxylates and benzoates and mixtures thereof. 8. Process according to any one of the preceding claims, characterized in that at least one of the comonomers in the first, second and/or third reactors is ethylene. 9. Process according to any of the preceding claims, characterized in that the comonomer in the first, second and/or third reactor is selected from ethylene only. 10. Method according to any one of the preceding claims, characterized in that a) the ratio of hydrogen/propylene (H ₂ /C ₃ ) in the first reactor is in the range from 1.5 to 6.0 mol/kmol; b) the ratio of hydrogen/propylene (H ₂ /C ₃ ) in the second reactor is in the range from 12.0 to 70.0 mol/kmol; And c) the ratio of hydrogen/propylene (H ₂ /C ₃ ) in the third reactor is in the range from 15.0 to 80.0 mol/kmol. 11. The method according to any one of the preceding claims, characterized in that the fraction of the third propylene polymer is extruded in the presence of an amount of at least one alpha nucleating agent in the range from 0.01 to 1.0 wt.%, based on the total amount of the polypropylene composition. 12. Polypropylene composition obtained by the method according to any one of claims 1-11, in which said one or more comonomers selected from ethylene and C ₄ -C ₁₀ alpha-olefins are introduced into the reactors in different quantities, resulting in a fraction of the third propylene polymer has a trimodal comonomer distribution with respect to the comonomer content of each of the propylene polymers contained in said third propylene polymer fraction. 13. Polypropylene composition according to claim 12, characterized in that the polypropylene composition - 15 042471 has a content of xylene soluble fraction (XCS) in the range from 5.5 to 18.0 wt.%, determined in accordance with ISO 16152 at 25°C. 14. Polypropylene composition according to any one of claims 12, 13, characterized in that the polypropylene composition has a melting point >152°C and a crystallization point >120°C, measured by DSC in accordance with ISO 11357/3. 15. Polypropylene composition according to any one of claims 12-14, characterized in that the polypropylene composition has a tensile modulus >950 MPa, measured in accordance with ISO 527-1:2012/ISO 527-2:2012 at 23°C injection molded test specimens. 16. A polypropylene composition according to any one of claims 12 to 15, characterized in that the polypropylene composition has a Charlie notched impact strength of >4.8 kJ/m ² measured in accordance with ISO 179/1 eA at 23° C. injection molded test specimens. 17. Polypropylene composition according to any one of claims 12-16, characterized in that the polypropylene composition has a haze value of <20%, measured in accordance with ASTM D1003 on injection molded plates 1 mm thick, manufactured as described in ENISO 1873 -2. 18. A closure cap containing a polypropylene composition according to any one of claims 12-17. Eurasian Patent Organization, EAPO Russia, 109012, Moscow, Maly Cherkassky per., 2