EA042998B1 - METHOD FOR PRODUCING POLYPROPYLENE COMPOSITION - Google Patents

Description

The present invention relates to a method for producing a polypropylene composition. More specifically, the present invention relates to a process for producing a polypropylene composition containing propylene and one or more comonomers selected from ethylene and C ₄ -C ₁₀ alpha-olefins, as well as to a polypropylene composition obtained by this method. The present invention further relates to an article containing said polypropylene composition.

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

In the field of packaging, it is very important to have a polypropylene composition with high flowability and good mechanical properties, i.e. with high tensile modulus and good impact resistance. High fluidity is necessary to achieve good processability in various product manufacturing methods, such as injection molding processes, which enables the high production speed typically required in the mass market. Mechanical properties are also important for this type of application, in particular in the field of producing containers that must contain contents such as foodstuffs or liquids contained therein. In addition, it is necessary that the containers have sufficient rigidity to be stackable.

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

Moreover, the haze of the product must be acceptable. In particular, a good balance between hardness and haze is required.

However, at least some of these properties may be achieved at the expense of another of these properties. For example, by increasing the melt flow rate, stiffness can be improved, but impact resistance properties are significantly degraded. Thus, the impact resistance and the melt flow index of the polypropylene composition are mutually opposed.

In addition, the high degree of crystallinity of the polypropylene composition makes it rather rigid, but also increases its haze. Thus, the balance between stiffness and haze of the polypropylene composition is of great importance.

Therefore, there is a general need for a process for the production of a polypropylene composition having a balanced combination of high fluidity, high stiffness and impact resistance, as well as a high level of optical properties (low haze value).

EP2539398 describes a process for producing a propylene random copolymer in a sequential polymerization process, and said process includes the steps of:

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

b) feeding the first polypropylene (PP1) into the second reactor (R2),

c) polymerization in a second reactor (R2) and in the presence of said first polypropylene (PP1), propylene and optionally at least one ethylene and/or C ₄ -C ₂₀ α-olefin to obtain a second polypropylene (PP2), wherein said 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 propylene random copolymer (RPP2),

d) feeding a mixture of the first polypropylene (PP1) and the second polypropylene (PP2) into the third reactor (R3), and

e) polymerization in the third reactor (R3) and in the presence of a mixture of the first polypropylene (PP1) and the second polypropylene (PP2), propylene and optionally at least one ethylene and/or C4-C20 α-olefin to obtain a third polypropylene (PP3), wherein said third polypropylene (PP3) is a second propylene homopolymer (H-PP2) or a third propylene random copolymer (R-PP3), wherein the first polypropylene (PP1), the second polypropylene (PP2) and the third polypropylene (PP3) form ( homogeneous) mixture.

However, the invention described in EP2539398 relates to pipes, hence the MFR ₂ of the obtained propylene random copolymer is from 0.5 to 10.0 g/10 min, and it may contain, in particular, beta-nucleating agents. In addition, EP2539398 lacks a description of the haze properties of the resulting propylene random copolymer.

EP2338657 relates to a heterophasic polypropylene composition with fairly high melt flow, high stiffness, acceptable impact properties, and an advantageous balance between stiffness and clarity. The described composition contains 30-60 wt.% fraction (A) propylene homopolymer, 10-50 wt.% fraction (B) propylene random copolymer, 1-20

- 1 042998 wt.% of fraction (C) of the first elastomeric copolymer of ethylene and propylene, 1-20 wt.% of fraction (D) of the second elastomeric copolymer of ethylene and propylene and 5-25 wt.% of fraction (E) of ethylene homo- or copolymer. This document does not describe haze values for 2 mm thick samples. In addition, the examples given do not contain an alpha nucleating agent. In addition, no granulation step is described for D1.

WO2012/126759 relates to thermoplastic polyolefin compositions having a good balance of mechanical and optical properties. The proposed composition of the random propylene copolymer contains 60-85 wt.% propylene copolymer and from 0.1 to 2 wt.% units formed from ethylene, and 15-40 wt.% propylene copolymer, and from 7 to 17 wt.% units, formed from ethylene, said composition having a total ethylene content of 3 to 4.5 wt.%, a melt flow index value according to ISO 1133(230/2.16) of 10 to 120 g/10 min. The document does not describe the presence of a propylene polymer (PP-c) with a comonomer content of 0.5-2.5% by weight.

WO2016/116606 relates to polypropylene bimodal random copolymer compositions having a good balance of mechanical and optical properties. It differs from the present invention in that it does not contain the polymer propylene (PP-c) with a comonomer content of 0.5-2.5% by weight.

The present invention is based on the discovery that the above-mentioned needs for a balanced combination of high fluidity, high stiffness and impact resistance, as well as a high level of optical properties (low haze value) can be met using a process for producing a special polypropylene composition. Thus, the present invention proposes a special method for obtaining a special polypropylene composition, including the steps:

a) polymerizing in a first reactor, preferably a slurry reactor, monomers containing propylene and optionally one or more comonomers selected from ethylene and C ₄ -C ₁₀ alpha-olefins, to obtain a first propylene polymer fraction having a comonomer content of 0.0 to 1.0 wt.%,

b) polymerizing in a second reactor, preferably a gas phase reactor, monomers containing 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 having a comonomer content from 4.5 to 20.0 wt.%,

c) granulating the second propylene polymer fraction,

d) melt-blending the granulated second propylene polymer fraction in the presence of:

i. a propylene polymer (PP-c) containing one or more comonomers selected from ethylene and C ₄ -C ₁₀ alpha-olefins, wherein the monomer content is from 0.5 to 2.5 wt.%, and ii. at least one alpha-nucleating agent, wherein said polypropylene composition has:

i - MFR ₂ from 11.0 to 60.0 g/10 min, measured in accordance with ISO 1133 at 230°C under a load of 2.16 kg, ii - haze value < 20%, measured in accordance with ASTM D1003 on cast pressure test specimens 1 mm thick prepared as described in EN ISO 1873-2.

The first and second fractions of the propylene polymer, in accordance with the present invention, are obtained in a sequential polymerization process in the presence of an olefin polymerization catalyst.

The term sequential polymerization process in the process for producing the first and second propylene polymer fractions means that the propylene polymer fractions are produced by a process comprising at least two reactors connected in series. In one preferred embodiment, the term sequential polymerization process in the process of obtaining the first and second fractions of the propylene polymer means that the reaction mixture from the first reactor, i. the first propylene polymer fraction with unreacted monomers is fed, preferably directly fed into the second reactor, where the second propylene polymer fraction is obtained.

Accordingly, in the sequential polymerization process to obtain the first and second fractions of the propylene polymer, in accordance with the present invention:

i - the first propylene polymer fraction obtained in the first reactor contains mainly the first propylene polymer (PP-a) which is obtained in said first reactor, ii - the second propylene polymer fraction obtained in the second reactor contains mainly a second propylene polymer (PP-b) which is produced in said second reactor.

Accordingly, the proposed method includes at least a first reactor and a second reactor. The proposed method may include at least one additional polymerization reactor located after the second reactor. In one particular embodiment, the process according to the present invention consists of two polymerization reactors, i.e. the first reactor and the second reactor. The term polymerization reactor means that the main polymerization reaction takes place. Thus, if a process consists of two or more polymerization reactors, this definition does not exclude the possibility that the process as a whole contains, for example, a prepolymerization step in a prepolymerization reactor. The term consists of is a limiting wording in relation to the main polymerization reactors. If the process according to the present invention generally comprises a prepolymerization reactor, then the term first propylene polymer fraction means the sum of the (co)polymer produced in the prepolymerization reactor and the (co)polymer produced in the first reactor.

Typically, the reactors are selected from slurry and gas phase reactors.

The first reactor is preferably a slurry reactor and can be any continuous reactor or a simple batch stirred tank reactor or a loop reactor operating in bulk or slurry polymerization mode. Bulk polymerization means a process in which the polymerization is carried out in liquid monomer, essentially in the absence of an inert diluent. However, it is known to those skilled in the art that monomers used for industrial production are never pure, and always contain aliphatic hydrocarbon impurities. For example, propylene monomer may contain up to 5% propane as an impurity. Thus, bulk polymerization preferably means a polymerization process in a reaction medium which contains at least 60% (w/w) monomer. In accordance with the present invention, the first reactor is more preferably a loop reactor.

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

The possible next polymerization reactor or reactors is/are preferably a gas phase reactor.

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

If the process according to the present invention generally comprises a prepolymerization reactor, said prepolymerization 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 prepolymerization reactor is smaller in size compared to the first reactor, the second reactor and the subsequent polymerization reactor or reactors according to 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 (co)polymerization of propylene in bulk or in suspension is carried out to obtain a (co)polymer of propylene.

The operating temperature in the prepolymerization reactor is 0 to 60°C, preferably 15 to 50°C, more preferably 18 to 35°C.

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 can be from 20 to 100 bar, preferably from 30 to 70 bar.

Hydrogen can be added to the prepolymerization reactor to control the molecular weight and hence the melt flow index of the MFR ₂ of the 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 there is a prepolymerization step in said process, the propylene (co)polymer produced in the prepolymerization reactor is also fed into the first reactor. In the first reactor, the first propylene polymer fraction is produced.

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

Typically, the first propylene polymer fraction has a melt flow index (MFR2) of 11 to 60 g/10 min, preferably 15 to 40 g/10 min, more preferably 17 to 35 g/10 min. MFR ₂ is determined in accordance with ISO 1133 at 230° C. and with a load of 2.16 kg.

The operating temperature in the first reactor is usually 62 to 85°C, preferably 65 to 82°C, more preferably 67 to 80°C.

Typically, the pressure in the first reactor is 20 to 80 bar, preferably 30 to 70 bar, more preferably 35 to 65 bar.

- 3 042998

Hydrogen can be added to the first reactor to control the molecular weight and hence the melt flow index MFR2 of the first propylene polymer fraction produced in the first reactor.

Typically, the hydrogen/propylene (H ₂ /C ₃ ) ratio in the first reactor is 1.5 to 6.0 mol/kmol, preferably 1.6 to 5.5 mol/kmol, more preferably 1.7 to 5, 0 mol/kmol.

Typically, 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 0.0 to 8.0 mol/kmol, more preferably 0 .0 to 7.5 mol/kmol.

Typically, the reaction mixture is fed from the first reactor, preferably directly into the second reactor. Served directly means a process in which the reaction mixture from the first reactor is sent directly to the next polymerization stage, i.e. to the second reactor. Monomers containing 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 second propylene polymer fraction is obtained.

The second propylene polymer fraction typically has a comonomer content selected from ethylene and C ₄ -C ₁₀ alpha-olefins of 4.5 to 20.0% by weight, preferably 4.7 to 17.0% by weight more preferably 4, 9 to 15.0 wt.% relative to the total amount of monomers present in the second fraction of the propylene polymer.

Typically, the second propylene polymer fraction has a melt flow index (MFR ₂ ) of 12 to 60 g/10 min, preferably 15 to 40 g/10 min, more preferably 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 70 to 95°C, preferably 75 to 90°C, more preferably 78 to 88°C.

Typically, the pressure in the second reactor is 5 to 50 bar, preferably 15 to 40 bar.

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

Typically, the hydrogen/propylene (H ₂ /C ₃ ) ratio in the second reactor is 15.0 to 80.0 mol/kmol, preferably 17.0 to 70.0 mol/kmol, more preferably 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 second reactor is from 45.0 to 200.0 mol/kmol, preferably from 50.0 to 180.0 mol/kmol, more preferably 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 (PP-a) is usually produced in an amount of 20 to 90% by weight, preferably in an amount of 25 to 85% by weight, more preferably in an amount of 30 to 80% by weight.

In the method according to the present invention, the propylene polymer obtained in the second reactor, i. the second propylene polymer (PP-b) is usually produced in an amount of 10 to 80% by weight, preferably in an amount of 15 to 75% by weight, more preferably in an amount of 20 to 70% by weight. The amount of the first propylene polymer (PP-a) and the second propylene polymer (PP-b) is expressed relative to the total amount of the first propylene polymer (PP-a) and the second propylene polymer (PP-b) contained in the second propylene polymer fraction.

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. , even more preferably selected from one or more comonomers containing ethylene, even more preferably said comonomer is selected from pure ethylene, in the context of the present invention.

After polymerization in the reactor in the second stage, the second fraction of the propylene polymer obtained in the second reactor is isolated by standard methods known to those skilled in the art. The isolated second propylene polymer fraction of the present invention is typically in particulate form.

Propylene polymer (PP-c) is typically produced in a polymerization process, such as a slurry polymerization process, a gas phase combination process, or a combination thereof, in the presence of an olefin polymerization catalyst.

In a preferred embodiment, the propylene polymer (PP-c) is produced in a sequential multi-pot polymerization process. The term sequential polymerization process means that the propylene polymer (PP-c) is obtained by a process comprising at least two reactors connected in series. Typically, the reactors are selected from slurry and gas phase reactors.

A more preferred polymerization process is a gas phase loop reactor process such as developed by Borealis and known as BORSTAR™ technology. Examples of such a polymerization process are described in EP0887379, WO92/12182, WO2004/000899, WO2004/111095, WO99/24478, WO99/24479 and WO00/68315.

- 4 042998

Typically, the catalyst for the polymerization of olefins is a Ziegler-Natta catalyst. Typically, a Ziegler-Natta polymerization catalyst contains one or more Group 4-6 transition metal (TM) compounds as defined by the IUPAC 2013 version, such as titanium, additionally 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 support such as, for example, silica or alumina. Alternatively, magnesium halide may form the solid support. It is also possible that the catalyst components are not supported on the outer support, but the catalyst is obtained by an emulsion curing method or a precipitation method, as is known to those skilled in the art of producing catalysts.

Preferably, the olefin polymerization catalyst is a particular type of Ziegler-Natta catalyst. In this particular type of Ziegler-Natta catalyst, it is important that the internal donor is not a phthalic compound. Preferably, no phthalate compounds are used during the whole process of making the special type of Ziegler-Natta catalyst, so that the finished special type Ziegler-Natta catalyst does not contain any phthalic compounds. Thus, a special type of Ziegler-Natta catalyst does not contain a phthalic compound. Therefore, the second fraction of the propylene polymer and the propylene polymer (PP-c) obtained in the presence of a special type of Ziegler-Natta catalyst do not contain a phthalic compound.

Typically, a special type Ziegler-Natta catalyst contains an internal donor (ID) which is a non-phthalate compound, and thus a special type Ziegler-Natta catalyst contains no phthalate compound at all. In addition, a special type of Ziegler-Natta catalyst may be a solid catalyst, preferably without an external support material such as silica or MgCl ₂ , and hence the solid catalyst is self-supporting.

The solid catalyst can be prepared in the following general way:

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 organic liquid reaction medium; or a ₂ ) at least an alkoxy compound of a Group 2 metal (Ax') which is a reaction product of a Group 2 metal compound and an alcoholic mixture of an alcohol (A) and a monohydric alcohol (B) of 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 a reaction product of a Group 2 metal compound and a monohydric alcohol (B), optionally in an organic liquid reaction medium; or a ₄ ) group 2 metal alkoxy compounds of the 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 _m', where M is a group 2 metal, X is halogen, R1 and R2 are different alkyl groups of 2-16 carbon atoms, and 0<n<2, 0<m<2, and n+m+(2-nm)=2, provided both n and m are not 0 at the same time, 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 particulate catalyst component, and adding a non-phthalate internal electron donor (ID) in at least one step prior to step c).

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

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

In the precipitation process in step b) the solution from step a) is combined with at least one transition metal compound and the entire reaction mixture is kept at at least 50°C, more preferably between 55 and 110°C, more preferably between 70 up to 100°C to ensure complete precipitation of the catalyst component in the form of solid particles of the catalyst component.

In the emulsion curing process of step b), the solution from step a) is usually added to at least one transition metal compound at a lower temperature, such as -10 to less than 50°C, preferably -5 to 30°C. During mixing, the emulsion is usually maintained at a temperature of from -10 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 usually carried out

- 5 042998 by heating the emulsion to a temperature of 70-150°C, preferably 80-110°C. According to the present invention, a catalyst obtained by an emulsion curing method is preferably used.

In step a), a solution of a ₂ ) or a ₃ ) is preferably 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 possibility is to prepare said magnesium alkoxy compounds separately, or they may even be commercially available as ready-made magnesium alkoxy compounds, and they can be used as such in the process for preparing the catalyst of the present invention.

Illustrative alcohols (A) are glycol monoethers. Preferred alcohols (A) are monoethers of C ₂ -C ₄ glycols, where the ether moieties contain 2 to 18 carbon atoms, preferably 4 to 12 carbon atoms. Preferred examples are 2-(2-ethylhexyloxy)ethanol, 2-butyloxyethanol, 2hexyloxyethanol and 1,3-propylene glycol monobutyl ether, 3-butoxy-2-proanol, with 2-(2-ethylhexyloxy)ethanol and monobutyl ether being particularly preferred. 1,3-propylene glycol, 3-butoxy-2-propanol.

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 C6 -C8 alkyl radical. The most preferred monohydric alcohol is 2-ethyl-1-hexanol or octanol.

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

The magnesium alkoxy compound may be the reaction product of an alcohol(s) as described above and a magnesium compound selected from dialkyl magnesium, alkyl magnesium alkoxides, magnesium dialkoxides, magnesium alkoxy halides, and alkyl magnesium halides. 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. Exemplary alkylmagnesium alkoxy compounds, when used, are ethylmagnesium butoxide, butylmagnesium pentoxide, octylmagnesium butoxide, and octylmagnesium octoxide. Preferably, dialkylmagnesium compounds are used. The most preferred dialkyl magnesium compounds are butyl octyl magnesium or butyl ethyl magnesium.

It is also possible that the magnesium compound reacts, in addition to alcohol (A) and alcohol (B), with a polyhydric alcohol (C) of the formula R(OH) _m to form said magnesium alkoxide compounds. Preferred polyhydric alcohols, when used, are those in which R is a straight, cyclic or branched C ₂ -C ₁₀ hydrocarbon residue and m is an integer from 2 to 6.

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

The solvent used to prepare the proposed catalyst may be selected from aromatic and aliphatic linear, branched and cyclic 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. Particularly preferred are hexanes and pentanes.

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

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

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

Hereinafter, the term derivative includes substituted compounds.

In an emulsion curing process, said two-phase liquid-liquid system can be obtained by simple mixing and optionally adding (additional) solvent(s) and/or additives such as a turbulence minimizing agent (TMA) and/or an emulsifying agent and/or an emulsion stabilizer , such as a surfactant, which are used as known in the art. These solvents and/or additives are used to facilitate the formation of the emulsion and/or to stabilize it. Preferably, the surfactants are acrylic or methacrylic polymers. Particular preference is given to linear C12-C20 (meth)acrylates such as, for example, poly(hexadecyl)methacrylate and poly(octadecyl)methacrylate, as well as mixtures thereof. The turbulence minimizing agent (TMA), when used, 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 preferably, it is polydecene.

The particulate solid product obtained by the emulsion precipitation or solidification process may be washed at least once, preferably at least twice, most preferably at least three times. Washing can be carried out with an aromatic and/or aliphatic hydrocarbon, preferably with toluene, heptane or pentane. Washing is also possible using TiCl ₄ , optionally in combination with an aromatic and/or aliphatic hydrocarbon. Wash solutions may also contain donors and/or Group 13 compounds such as trialkyl aluminum, halogenated alkyl aluminum compounds or alkoxy aluminum compounds. Aluminum compounds can also be added during catalyst synthesis. The catalyst may then be dried, for example by evaporation or nitrogen purge, or may be suspended in an oily liquid without a drying step.

The final special type of Ziegler-Natta catalyst is preferably obtained in the form of particles, typically having an average particle size range of 5 to 200 µm, preferably 10 to 100 µm. These particles are usually tightly packed with a low degree of 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 1 to 6 wt%, the amount of Mg is 10 to 20 wt%, and the amount of internal donor present in the catalyst is 10 to 40 wt% of the catalyst composition. A detailed description of the preparation of the catalysts used according to the present invention is presented in WO2012/007430, EP2610271 and EP2610272.

The external donor (ED) is preferably present as an additional component in the polymerization processes of the present invention. Suitable external donors (ED) include certain silanes, ethers, esters, amines, ketones, heterocyclic compounds, and mixtures thereof. It is particularly preferred to use a silane. It is most preferred to use silanes of general formula (I)

R ^a pR ^b qSi(OR ^c )( ₄ . _P . _q) (I) where R ^a , R ^b and R ^c are a hydrocarbon radical, in particular an alkyl or cycloalkyl group, and where p and q are numbers from 0 up 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 different. Specific examples of silanes according to formula (I) are (tert-butyl) ₂ Si(OCH ₃ ) ₂ , (cyclohexyl)(methyl)Si(OCH ₃ ) ₂ , (phenyl) ₂ Si(OCH ₃ ) ₂ and ( cyclonentyl) ₂ Si(OCH ₃ ) ₂ . Another most preferred silane corresponds to the general formula (II)

Si(OCH ₂ CH ₃ ) ₃ (NR ³ R ⁴ ) (II) where R ³ and R ⁴ may be the same or different and represent a linear, branched or cyclic hydrocarbon group containing from 1 to 12 carbon atoms. Particularly preferably, 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, t-amyl, neopentyl, cyclopentyl, cyclohexyl, methylcyclopentyl and cycloheptyl. Most preferably, ethyl is used.

Typically, in addition to a Ziegler-Natta catalyst or a specific type of Ziegler-Natta catalyst and an optional external donor (ED), a co-catalyst (Co) may be present in the polymerization processes of the present invention. The co-catalyst is preferably a Group 13 compound (IUPAC 2013 version) such as, for example, an aluminum compound, such as an organoaluminum compound or an aluminum halide compound. 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).

As a general rule, the molar ratio between cocatalyst (Co) and

- 7 042998 external donor (ED) [Co/ED] and/or the molar ratio between co-catalyst (Co) and transition metal (TM) [Co/TM]. The molar ratio between cocatalyst (Co) and 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 specified upper and lower range values are inclusive.

The molar 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 specified upper and lower range values are inclusive.

In accordance with the present invention, the second fraction of the propylene polymer separated from the polymerization process is usually melt blended in the presence of additives.

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

After the melt blending step, the resulting second melt blended propylene polymer fraction is granulated, for example in an underwater granulator or by solidifying one or more strands in a water bath in a conventional granulator.

In accordance with the present invention, the granular second fraction of propylene polymer is melt blended in the presence of

i. a propylene polymer (PP-c) containing one or more comonomers selected from ethylene and C4-C10 alpha-olefins, wherein the monomer content is from 0.5 to 2.5% by weight, and ii. at least one alpha-nucleating agent, to obtain a polypropylene composition according to the present invention.

The propylene polymer (PP-c) according to the present invention is usually a propylene copolymer.

The propylene polymer (PP-c) typically contains one or more comonomers selected from ethylene and C4-C10 alpha olefins, preferably selected from ethylene and C ₄ -C ₈ alpha olefins, more preferably selected from ethylene and C4-C6 alpha olefins, even more preferably selected from one or more comonomers containing ethylene, even more preferably said comonomer is selected from pure ethylene.

The propylene polymer (PP-c) according to the present invention generally has a comonomer content of 0.5 to 2.5 wt%, preferably 0.6 to 2.0 wt%, more preferably 0.7 to 1.8 wt% relative to the total amount of monomers present in the propylene polymer.

Typically, the propylene polymer (PP-c) has a melt flow index (MFR ₂ ) of 11 to 60 g/10 min, preferably 15 to 40 g/10 min, more preferably 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 alpha nucleating agent is typically selected from the group consisting of:

(i) salts of monocarboxylic acids and polycarboxylic acids, for example sodium benzoate or aluminum tert-butylbenzoate, (ii) dibenzylidene sorbitol (for example, 1,3:2,4-dibenzylidene sorbitol) and C1-C ₈ -alkyl-substituted derivatives of dibenzylidene sorbitol, such as methyldibenzylidene sorbitol , ethyldibenzylidene sorbitol or dimethyldibenzylidene sorbitol (e.g. 1,3:2,4-di(methylbenzylidene)sorbitol), or substituted nonit derivatives such as 1,2,3-trideoxy-4,6:5,7-bis-O-[ (4-propylphenyl)methylene]nonit, (iii) salts of diesters of phosphoric acid, for example sodium 2,2'-methylenebis(4,6-di-tert-butylphenyl)phosphate or hydroxy-bis[2,2'-methylene-bis (4,6-di-tert-butylphenyl)phosphate]aluminum, (iv) vinylcycloalkane polymers and vinylalkane polymers, and

- 8 042998 (v) their mixtures.

Preferably, the alpha-nucleating agent is dibenzylidene sorbitol (eg 1,3:2,4-dibenzylidene sorbitol) or a C ₁ -C ₈ alkyl-substituted derivative of dibenzylidene sorbitol such as methyldibenzylidene sorbitol, ethyldibenzylidene sorbitol or dimethyldibenzylidene sorbitol (eg 1.3:2 ,4-di(methylbenzylidene)sorbitol), or a substituted nonite derivative such as 1,2,3-trideoxy4,6:5,7-bis-O-[(4-propylphenyl)methylene]nonite.

In accordance with the present invention, typically from 15 to 84 wt.% of the granular second fraction of propylene polymer is melt-blended in the presence of 15-84 wt.% of propylene polymer (PP-c) and 0.01-1.0 wt.% of at least at least one alpha-nucleating agent relative to the total amount of the granular second fraction of propylene polymer, propylene polymer (PP-c) and at least one alpha-nucleating agent.

Preferably, from 18 to 79.1 wt.% of the granular second fraction of propylene polymer is melt-blended in the presence of 20-81.1 wt.% of propylene polymer (PP-c) and 0.03-0.90 wt.% of at least one alpha-nucleating agent relative to the total amount of the granular second fraction of propylene polymer, propylene polymer (PP-c) and at least one alpha-nucleating agent.

More preferably, from 20 to 74.2 wt.% of the granular second fraction of propylene polymer is melt-blended in the presence of 25-79.2 wt.% of propylene polymer (PP-c) and 0.05-0.80 wt.% of at least at least one alpha-nucleating agent relative to the total amount of the granular second fraction of propylene polymer, propylene polymer (PP-c) and at least one alpha-nucleating agent.

Melt blending of the granulated propylene polymer second fraction with the propylene polymer (PP-c) and at least one alpha-nucleating agent is typically carried out in a continuous melt mixing device such as, for example, an extruder or a unidirectional kneader. The melt mixing device may include a loading area, a kneading area, and a mouthpiece area.

Typically, the melt mixing devices maintain a certain temperature profile along the screw.

Melt blending of the granulated second propylene polymer with the propylene polymer (PP-c) and at least one alpha-nucleating agent is preferably carried out in an extruder.

The extruder 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 contains a loading zone, a melting zone, a mixing zone, and a die zone. An extruder, as is known to those skilled in the art, is usually made up of cylindrical parts that are located in the above zones of the extruder.

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

Loading Zone.

The granular propylene polymer second cut, propylene polymer (PP-c) and at least one alpha nucleating agent are typically introduced into the extruder through the feed zone. The loading zone feeds the granular second fraction of propylene polymer, propylene polymer (PP-c) and at least one alpha-nucleating agent to the melting zone. As a rule, the melting zone consists of a feed funnel and a connecting pipe connecting the funnel with the melting zone. Typically, the granular propylene polymer second cut, propylene polymer (PP-c), and at least one alpha-nucleating agent pass through the loading zone under the action of gravity, i.e. usually down.

In a preferred embodiment, the implementation of at least one alpha-nucleating agent wholly or partially fed through one or more feed holes located in the extruder, for example, through a side feed mechanism.

melting zone.

Typically, a mixture of the granulated propylene polymer second cut, propylene polymer (PP-c) and at least one alpha nucleating agent is passed from the feed zone to the melt zone. In the melting zone, the mixture melts.

mixing zone.

After the melting zone, the molten mixture enters the mixing zone. The screw in the mixing zone usually contains one or more mixing sections, which contain screw elements that provide a certain amount of reverse flow.

- 9 042998

The mixing zone may contain additional elements such as a throttle valve or a worm pump.

Mouthpiece area.

The die area typically contains the extruder head. There are no restrictions regarding the design of the extruder head.

In the method according to the present invention, the granular fraction of the second propylene polymer, propylene polymer (PP-c) and at least one alpha-nucleating agent are usually melt-blended at a temperature of from 190 to 260°C, preferably from 200 to 250°C.

Those skilled in the art are familiar with the screw speed of an extruder and can readily determine a suitable screw speed. Typically, the screw speed is controlled to a range of 100 to 750 revolutions per minute (rpm), preferably 150 to 650 rpm.

The extruder may also have one or more feed ports for supplying additional components, such as, for example, other polymers or additives, to the extruder. 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 scavengers, aromatic amines, hindered amine stabilizers, or mixtures thereof), metal deactivators (e.g., Irganox® MD 1024) or UV stabilizers (e.g. hindered amine light stabilizers). Other types of additives are modifiers such as antistatic or antifogging agents (for example, ethoxylated amines and glycerol ester amides), acid neutralizers (for example, Ca stearate), foaming agents, cohesive agents (for example, polyisobutene), lubricants, and resins (e.g. ionomer waxes, waxes based on polyethylene and ethylene copolymers, Fischer-Tropsch waxes, montan waxes, fluorine-containing compounds or paraffin waxes), as well as slip and anti-blocking agents (e.g. erucamide, oleamide, talc, natural silica and synthetic dioxide silicon or zeolites), as well as mixtures thereof.

As a rule, the total amount of additives introduced into the extruder during melt mixing of the granular fraction of the second propylene polymer, propylene polymer (PP-c) and at least one alpha-nucleating agent according to 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 expressed relative to the total amount of polypropylene composition introduced into the extruder.

At the end of the extruder, a melt of the polypropylene composition is obtained. The melt of the polypropylene composition of the present invention is then passed through the die in an optional region of the extruder die. When passing the melt of the polypropylene composition according to the present invention through the extruder die, additional cooling and granulation is usually carried out.

The mouthpiece area usually contains a die plate, which is usually a thick metal disk with many holes. The holes are parallel to the axis of the screw.

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

The present invention also provides a polypropylene composition that can be obtained, preferably obtained by the method according to the present invention.

The polypropylene composition, which can be obtained, preferably obtained by the method according to the present invention, usually contains one or more comonomers 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, even more preferably selected from one or more comonomers containing ethylene, even more preferably said comonomer is selected from pure ethylene.

The polypropylene composition that can be obtained, preferably obtained by the method according to the present invention, usually has a comonomer content of from 1.5 to 5.0 wt.%, preferably from 1.6 to 4.0 wt.%, more preferably from 1.7 up to 3.5% mol. The comonomer content is expressed relative to the total amount of monomers present in the polypropylene composition.

Generally, the polypropylene composition that can be produced, preferably obtained by the process of the present invention, has a melt flow index (MFR ₂ ) of 12 to 60 g/10 min, preferably 15 to 40 g/10 min, more preferably 17 to 35 g/10 min. MFR ₂ is determined in accordance with ISO 1133 at 230° C. and with a load of 2.16 kg.

Typically, the polypropylene composition that can be obtained, preferably obtained by the method according to the present invention, has a haze value of <20%, preferably from 2 to 28%, more preferably from 3 to 17%. The haze value is measured in accordance with ASTM D1003 on 1 mm thick injection molded specimens prepared as described in EN ISO 1873-2.

- 10 042998

In general, the polypropylene composition that can be obtained, preferably obtained by the method according to the present invention, has a melting point of >152°C, preferably from 153 to 163°C, more preferably from 154 to 162°C, even more preferably from 154 to

160°C. The melting point (M.p.) is measured by DSC in accordance with ISO 11357/3.

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

In general, the polypropylene composition that can be obtained, preferably obtained by the method according to the present invention, has a content of xylene soluble substances (XCS) of 5.5 to 18.0 wt.%, preferably from 6.0 to 16.0 wt. %, more preferably from 6.2 to 15.0 wt.%. The proportion of compounds soluble in xylene is determined according to ISO 16152 at 25°C.

In general, the polypropylene composition that can be obtained, preferably obtained by the method of the present invention, has tensile resiliences >950 MPa, preferably 951 to 1600 MPa, more preferably 1000 to 1600 MPa, even more preferably 1050 to 1550 MPa. Tensile modulus is measured according to ISO 5271:2012/ISO 527-2:2012 at 23° C. on injection molded test specimens.

Generally, the polypropylene composition that can be produced, preferably obtained by the method of the present invention, has a Charpy notched impact strength >4.8 kJ/m ² , preferably 4.9 to 20.0 kJ/m ² , more preferably from 5.0 to 15.0 kJ/m ² , even more preferably from 5.0 to 13.0 kJ/m ² , even more preferably from 7.0 to 13 kJ/m ² . 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.

The present invention also provides an article containing a polypropylene composition, which can be obtained, preferably obtained by the method according to the present invention. Suitable products are films, such as, for example, cast films, and injection molded products. A preferred product is a closure, screw cap or closure system for food or liquid packaging.

Finally, the present invention relates to the use of a polypropylene composition which can be obtained, preferably obtained by the method according to the present invention, in the production of a cast film or molded article, preferably a closure, screw cap or closure system for food or liquid packaging. A fluid is usually defined as a substance that continuously deforms (flows) under the action of an applied shear stress.

Examples

I. Measurement methods.

a) Melt flow index.

The melt flow index (MFR) is determined according to ISO 1133 and is reported in g/10 min. The MFR is an indicator of the fluidity and hence the processability of a polymer. The higher the melt flow index, the lower the viscosity of the polymer. The MFR ₂ of polypropylene is determined at 230° C. and under a load of 2.16 kg.

b) DSC analysis.

Melting point and crystallization temperature are measured on a differential scanning calorimeter (DSC) TA Instrument Q2000 in accordance with ISO 11357/3 on samples weighing 5-10 mg, in a nitrogen flow of 50 ml/min. The crystallization and melting temperatures were recorded in a heating/cooling/heating cycle at a scan rate of 10°C/min from 30 to 225°C. Crystallization and melting temperatures were recorded as peaks of endotherms and exotherms in the cooling stage and in the second heating stage, respectively.

c) The content of compounds soluble in xylene (XCS, wt.%).

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

d) Tensile modulus.

Tensile modulus is measured according to ISO 527-1:2012/ISO 527-2:2012 at 23° C. and slider speed = 50 mm/min; using test specimens obtained by injection molding as described in EN ISO 1873-2 (dumbbell-shaped specimen, 4 mm thick).

e) Charpy notch impact resistance.

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 (80x10x4 mm).

f) Turbidity.

Haze value is measured in accordance with ASTM D1003 on injection molded specimens

- 11 042998 with a thickness of 1 mm and an area of 60x60 mm ² obtained as described in EN ISO 1873-2.

g) Comonomer content.

Ethylene content of poly(propylene-co-ethylene) measured by IR spectroscopy

Quantitative infrared (IR) spectroscopy was used to quantify the ethylene content of poly(ethylene-co-propene) copolymers, based on the calibration for the primary method.

Calibration was performed using a set of proprietary, non-commercial calibration standards with known ethylene content, determined by quantitative ¹³ C nuclear magnetic resonance (NMR) spectroscopy in solution. The calibration procedure was carried out in the usual way, described in detail in the literature. The calibration set consisted of 38 calibration standards with an ethylene content from 0.2 to 75.0 wt.%, obtained in a pilot plant or in a full-scale plant under different conditions. The calibration set was chosen to reflect the typical variety of copolymers found by quantitative IR spectroscopy. Quantitative IR spectra were recorded in the solid state on a Bruker Vertex 70 IR spectrometer with Fourier transform. The spectra were recorded on square film samples 25x25 mm, 300 μm thick, obtained by pressing in a mold at 180–210°C and 4–6 MPa. Film samples 100 µm thick with a very high ethylene content (>50 mol %) were used. We used standard Fourier transform transmission IR spectroscopy in the spectral range 5000-500 cm ^-1 , with an aperture of 6 mm, a spectral resolution of 2 cm ^-1 , 16 background scans, 16 spectrum scans, a factor of 64 filling the inferogram with zeros and with apodization by the three-term Blackman- Harris.

Quantitative analysis was carried out using the total area of vibrational deformations of CH ₂ at 730 and 720 cm ^-1 (Aq), corresponding to structural units (CH2)>2 (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 CH units (G integration method, limits 4650, 4007 cm ^-1 ). Then, based on the normalized absorbance (Aq/A _r ), the ethylene content was predicted in terms of mass percent using a quadratic calibration curve. A calibration curve was pre-formed by conventional least squares regression (OLS) of normalized absorbance values, and the primary comonomer content was measured from the calibration set.

Ethylene content of poly(propylene-co-ethylene) 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 were recorded using a ^-optimized 10 mm measuring head for an extended temperature range at 125° C. using nitrogen gas in pneumatic instruments. 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 initially preparing the sample in the thermoblock, the NMR vial was further heated in a rotary hearth furnace for at least 1 hour. After being placed in a magnet, the ampoule was rotated at 10 Hz. This setting was chosen mainly because of the need for high resolution and accurate quantification of ethylene content. Standard single-pulse excitation without NOE was used using an optimized tip angle, a 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). In general, 6144 (6 thousand) transitions were recorded for one spectrum. Quantitative 13C{1H} 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 using the chemical shift of the solvent. This approach allows comparison with the standard even in the absence of this structural unit. The characteristic signals corresponding to ethylene incorporation were observed (Cheng, HN, Macromolecules 17 (1984), 1950) and the comonomer content was calculated as the proportion of ethylene in the polymer relative to the total monomer in the polymer: fE=(E/(P+E). Comonomer fraction content was quantified by the method of Wang et al (Wang, WJ., Zhu, S., Macromolecules 33 (2000), 1157) by integrating several signals over the entire spectral region on the ¹³ C{1H} spectrum.This method was chosen due to its reliability and The integral regions were slightly adjusted to improve applicability over the entire range of comonomer abundances encountered For systems in which only isolated ethylene was observed in PPEPP sequences, the method of Wang et al. was modified to reduce the impact of integrating known missing positions. approach reduces the overestimation of the ethylene content in these systems and is implemented by reducing the number of positions used to determine the absolute

- 12 042998 ethylene content, up to the formula E=0.5(Sββ+Sβγ+Sβδ+0.5(Sαβ+Sαγ)). When using the specified set of positions, the corresponding integral equation becomes: E=0.5(IH+I _G +0.5(I _C +ID)), using the notation adopted in Wang et al. (Wang, WJ., Zhu, S., Macromolecules 33 (2000), 1157). The equations used to determine the absolute propylene content were not modified. The molar percentage of comonomer incorporation was calculated from the mole fraction: E[mol.%]=100*fE. The mass percentage of comonomer incorporation was calculated from the molar fraction: E[wt%]=100*(fE*28.06)/((fE*28.06)+((1-fE)*42.08)).

II. Examples according to the invention and comparative examples.

a) Obtaining a catalyst.

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 liter reactor. Then, 7.8 liters of a 20.0% toluene solution of BEM (butylethylmagnesium) manufactured by Crompton GmbH was slowly added to the rapidly 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 Mg alkoxide prepared as described above was mixed with 4.0 ml of bis(2ethylhexyl)citraconate for 5 minutes. After mixing, the resulting Mg complex was immediately used to prepare a catalyst component.

In a reactor with a volume of 300 ml, equipped with a mechanical stirrer, was placed 19.5 ml of titanium tetrachloride at 25.0°C. The stirring speed was adjusted to 170 rpm. 26.0 g of the Mg complex obtained as described above was added over 30 minutes, maintaining the temperature at 25.0°C. 3.0 ml of Viscoplex® 1-254 and 1.0 ml of a toluene solution with 2 mg of Necadd 447™ were added. Then 24.0 ml of heptane was added to form an emulsion. Mixing was continued for 30 minutes at 25.0°C, after which the reactor temperature was raised to 90.0°C in 30 minutes. The reaction mixture was stirred for another 30 minutes at 90.0°C. Then stopped stirring and left the reaction mixture to settle for 15 minutes at 90.0°C. The solid was washed 5 times: Wash solutions were prepared at 80.0° C. with stirring for 30 minutes at 170 rpm. After stopping stirring, the reaction mixture was left to settle for 20-30 minutes and then passed through a siphon.

Wash 1: Wash solution was prepared from a mixture of 100 ml of toluene and 1 ml of donor.

Wash 2: Wash solution was prepared from a mixture of 30 ml TiCl ₄ and 1 ml donor.

Wash 3: The wash solution was prepared from 100 ml of toluene.

Wash 4: The wash solution was prepared from 60 ml of heptane.

Wash 5: A wash solution was prepared from 60 ml heptane with stirring for 10 minutes.

Then the stirring was stopped and the reaction mixture was left to stand for 10 minutes while lowering the temperature to 70°C, followed by passing through a siphon, followed by blowing N ₂ for 20 minutes to obtain an air-sensitive powder.

b) Examples according to the invention (IE1, IE2 and IE3).

The second fraction of the propylene polymer, as well as the propylene polymer (PP-c) for the examples according to the present invention (IE1, IE2 and IE3) was obtained in a pilot plant with a prepolymerization reactor, one slurry loop reactor and one gas phase reactor. To obtain a second cut of propylene polymer and propylene polymer (PP-c), the solid catalyst component described above was used along with triethylaluminum (TEAL) as a co-catalyst and dicyclopentyldimethoxysilane (D-donor) as an external donor, respectively.

The conditions of the polymerization process and the properties of the second fraction of the propylene polymer and propylene polymer (PP-c) are described in table. 1.

Polypropylene compositions according to the present invention were obtained by extruding an appropriate amount of the second fraction of propylene polymer, propylene polymer (PP-c) and nucleating agent in a co-rotating twin screw extruder type Coperion ZSK 40 (screw diameter 40 mm, ratio L/D 38). The temperature in the extruder was 190-230°C. In each example according to the present invention, 0.05 wt.% Irganox 1010 (pentaerythrityl-tetrakis(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, 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 tradename Grindsted PS 426 from Danisco A/S, Denmark).

After the extrusion step and after the strands had solidified 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.

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c) Comparative examples (CE1 and CE2).

CE-1 is a C ₂ propylene random copolymer having an MFR2 of 13.0 g/10 min, prepared in a one pot process and commercially available from Borealis under the tradename RE420MO.

CE-2 is a C ₂ propylene random copolymer having an MFR ₂ of 20.0 g/10 min, prepared in a one pot process and commercially available from Borealis under the tradename RF365MO.

Table 1

Preparation and properties of the second fraction of propylene polymer and propylene polymer (PP-c)

The second fraction of propylene polymer Propylene polymer (PP-s) Prepolymerization reactor Temperature [°C] thirty thirty Catalyst supply [g/h] 3.0 2.9 D-donor [g/t propylene] 41.1 41.1 TEA1_/propylene [g/t propylene] 170 170 Al/D-Donor [Co/ED] [mol/mol] 8.3 8.2 Al/Ti [Co/TM] [mol/mol] 217 216 Time of stay [h] 0.3 0.3 loop reactor Temperature [°C] 70 70 Pressure [kPa] 5270 5380 Time of stay [h] 0.4 0.4 Split [%] 56 64 Ratio H ₂ /Cz [mol/kmol] 1.7 1.8 C ₂ / Cz ratio [mol/kmol] 3.1 3.1 PTR ₂ [g/10 min] 19 21 Content C ₂ [wt%] 0.5 0.5 gas phase reactor Temperature [°C] 80 80 Pressure [kPa] 1900 1820 Time of stay [h] 1.4 1.4 Split [%] 44 36 Ratio H ₂ /Cz [mol/kmol] 45.9 27.4 C ₂ / Cz ratio [mol/kmol] 62.9 8.5 PTR ₂ [g/10 min] 20 22 Content C ₂ [wt%] 4.5 1.0

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

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table 2

Extrusion process conditions and properties of the polypropylene composition

IE1 IE2 IE3 CE1 CE2 The second fraction of propylene polymer [wt%] 59.6 42.0 22.0 0.0 0.0 Propylene polymer (PP-s) [wt%] 40.0 57.6 77.6 0.0 0.0 Nucleating agent (Millad 3988®) [wt%] 0.2 0.2 0.2 0.0 0.0 Composition Properties* PTR ₂ [g/10 min] 21.0 20.0 22.0 13.0 20.0 Content C ₂ [wt%] 3.0 2.4 1.7 3.4 3.4 XCS [wt%] 11.4 9.1 6.5 5.8 6.8 Tensile modulus [MPa] 1256 1397 1573 921 1138 Charly notched impact strength at 23°C [kJ / m ² ] 7.0 5.6 4.9 5.3 4.5 Haze (1 mm) [%] 17 18 18 23 20 Tm. [°C] 160 160 160 150 151 Tkrist. [°C] 127 128 127 120 120

* Measured on pellets obtained after the extrusion process.

Based on the table. 2, it can be concluded that the polypropylene compositions (samples of this invention) show an improved balance of high flow, high stiffness and impact resistance, as well as a high level of optical properties (low haze value), compared to the comparative examples.

Claims (16)

1. A method for producing a polypropylene composition by sequential polymerization, including the steps: a) polymerizing in the first reactor the propylene-containing monomers to obtain a first propylene polymer fraction having a comonomer content of from 0.0 to 1.0 wt.%, where the comonomer present is one or more comonomers selected from ethylene and C ₄ - C ₁₀ alpha olefins, b) polymerizing in a second reactor monomers containing 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 having a comonomer content of 4.5 to 20.0 wt.%, c) granulating the second propylene polymer fraction, d) melt-blending the granulated second propylene polymer fraction in the presence of i. propylene polymer (PP-c) obtained by a process comprising at least two reactors connected in series, containing one or more comonomers selected from ethylene and C ₄ C ₁₀ alpha-olefins, the comonomer content being from 0.5 to 2, 5 wt.%, and ii. at least one alpha-nucleating agent, wherein said polypropylene composition has i - MFI ₂ from 11.0 to 60.0 g/10 min, measured in accordance with ISO 1133 at 230°C under a load of 2.16 kg, ii - haze value <20% measured according to ASTM D1003 on 1 mm thick injection molded specimens prepared as described in EN ISO 1873-2; iii - from 15 to 84 wt.% granulated second polymer fraction relative to the total amount of polypropylene composition; iv - from 15 to 84 wt.% of the propylene polymer (PP-c) relative to the total amount of the polypropylene composition; v - from 0.01 to 1.0 wt.% at least one alpha-nucleating agent relative to the total amount of the polypropylene composition; and vi - where the first propylene polymer fraction is obtained in an amount of from 20 to 90 wt.% relative to the total amount of the first propylene polymer and the second propylene polymer contained in the second propylene polymer fraction. 2. The method according to claim 1, characterized in that the polypropylene composition has a comonomer content of from 1.5 to 5.0 wt.% relative to the total amount of monomers present in the polypropylene - 15 042998 linen composition. 3. Process according to any one of the preceding claims, characterized in that the melt blending of the granulated second propylene polymer fraction is carried out at a temperature of 190 to 260°C. 4. Process according to any one of the preceding claims, characterized in that the melt blending of the granulated second propylene polymer fraction is carried out in a single screw extruder or in a twin screw extruder. 5. Process according to any of the preceding claims, characterized in that the second propylene polymer fraction and the propylene polymer (PP-c) do not contain a phthalic compound. 6. Process according to any one of the preceding claims, characterized in that said first reactor is a slurry reactor. 7. Process according to any one of the preceding claims, characterized in that said second reactor is a gas phase reactor. 8. Process according to any one of the preceding claims, characterized in that in step a) monomers containing propylene and one or more comonomers selected from ethylene and C4-C10 alpha-olefins are polymerized. 9. Polypropylene composition obtained by the method according to any one of claims 1 to 8, where the polypropylene composition has i - MFI ₂ from 11.0 to 60.0 g/10 min, measured in accordance with ISO 1133 at 230°C under load 2 .16 kg, ii - haze value < 20%, measured in accordance with ASTM D1003 on 1 mm thick injection molded specimens obtained as described in EN ISO 1873-2. 10. A polypropylene composition according to claim 9, characterized in that said polypropylene composition has a content of xylene-soluble compounds (XCS) of 5.5 to 18.0% by weight, determined according to ISO 16152 at 25°C. 11. Polypropylene composition according to any one of claims 9, 10, characterized in that said polypropylene composition has a melting point >152°C and a crystallization temperature >120°C, measured in accordance with ISO 11357/3. 12. A polypropylene composition according to any one of claims 9 to 11, characterized in that said polypropylene composition has a tensile modulus >950 MPa, measured in accordance with ISO 527-1:2012/ISO 527-2:2012 on experimental samples, injection molded at 23°C. 13. A polypropylene composition according to any one of claims 9 to 12, characterized in that said 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. experimental samples obtained by injection molding, as described in EN ISO 1873-2. 14. A polypropylene composition according to any one of claims 9 to 13, characterized in that said polypropylene composition does not contain a phthalic compound. 15. An article containing a polypropylene composition according to any of claims 9 to 14, wherein said article is a cast film, injection molded article, closure, screw cap, or closure system for food or liquid packaging. 16. The use of a polypropylene composition according to any one of claims 9 to 14 for producing an article selected from a cast film, an injection molded article, a closure cap, a screw cap, or a closure system for food or liquid packaging.