RU2776211C9 - Propylene random copolymer for use in films - Google Patents

Abstract

FIELD: polymers.

SUBSTANCE: invention relates to a polypropylene composition (P) for a sealing layer in a multilayer film comprising at least 90.0% wt., as calculated for the total weight of the polypropylene composition (P), of a copolymer (C) of propylene and 1-hexene with i) a total content of 1-hexene in the range from 2.0 to 10.0% wt., ii) a melt flow index MFI2, as determined in accordance with ISO 1133 (2.16 kg, 230°C), in the range from 4.0 to 20.0 g/10 min, and iii) 2.1-erythro-regiodefects in the amount of at least 0.2% mol. The copolymer (C) is therein subjected to visbreaking with a visbreaking ratio (VR) in the range from 1.5 to 15.0, wherein visbreaking is determined in accordance with the equation (2) VR = MFIend/MFIstart (2), wherein MFIend constitutes the melt flow index MFI2, as determined in accordance with ISO 1133 (230°C, 2.16 kg), of the copolymer (C) after visbreaking, and MFIstart constitutes the melt flow index MFI2, as determined in accordance with ISO 1133 (230°C, 2.16 kg), of the copolymer (C) before visbreaking. The proposed copolymer has low turbidity while maintaining a high level of sealing and mechanical properties. The invention also relates to a method for producing a copolymer, a polypropylene composition, a film, and an application of the film as a sealing layer.

EFFECT: creation of a low-turbidity copolymer applicable in films.

17 cl, 1 tbl, 1 ex

Description

The invention relates to a polypropylene composition (P) comprising a bimodal copolymer of propylene and 1-hexene, obtained in the presence of a metallocene catalyst, and the specified bimodal copolymer (C) has a melt flow index MFR ₂ in the range from 4.0 to 20.0 g/10 min. In addition, the invention relates to a method for producing a copolymer (C) and to an article comprising said polypropylene composition (P).

Polypropylene is widely used in various applications such as cast films and cast film seals. Commonly used polypropylenes for use in seal layers are terpolymers (terpolymers) of propylene, ethylene and butene (C2C3C4) or propylene-ethylene random copolymers prepared in the presence of Ziegler-Natta catalysts. Typically, the melt flow rate of such polypropylenes is in the range of 4.0 to about 20.0 g/10 min. In order to achieve a melt flow index within the specified range, the polymerization conditions in the reactor can be appropriately adjusted by adjusting the amount of hydrogen supplied to the reactor. However, according to this approach, when the range of the melt flow index changes during the process, a lot of waste is produced.

Another method is to use controlled rheology (visbreaking) technology, meaning that radical initiators are introduced in the compounding step and the final melt flow index is achieved by breaking the chain with the initially low melt flow index. As a rule, the initiators are peroxides. They break down into radicals at elevated temperatures, which triggers polypropylene chain scission during processing. This on the one hand reduces complexity and waste production, however, on the other hand it is known that oligomers will be obtained which can cause problems for some applications. For example, sterilization properties will be worse, i.e. higher turbidity after sterilization, or more leachables will be obtained.

Accordingly, there is a need in the art for a propylene copolymer that is applicable as a sealing layer of a multilayer film and at the same time can be sterilized without degrading optical properties.

In addition to optical properties, the sealing properties of polypropylene films used for packaging applications are also required to be at a high level. For the sealing process, it is essential that the films have a wide sealing window (interval), i.e. the temperature window for sealing should be as wide as possible. In addition, the product to be sealed should not be subjected to high temperatures, for which a low seal start temperature (TNG) is preferred. In addition, a high hot tack strength is required to ensure the formation of a strong seal. EP 2386603 A1 describes cast films made from copolymers of propylene and higher α-olefins showing a wide seal window at a low seal start temperature (SIT). Propylene-1-hexene copolymers showing improved hot tack properties in combination with a good seal window are also disclosed in WO 2011/131639 A1. However, the optical properties are not satisfactory.

Accordingly, the subject of the invention is to obtain a propylene copolymer with low turbidity before and after sterilization, while maintaining a high level of sealing and mechanical properties.

Thus, the invention proposes a polypropylene composition (P) comprising at least 90.0 wt. %, based on the total weight of the polypropylene composition (P), copolymer (C) of propylene and 1-hexene, having

i) the total content of 1-hexene in the range from 2.0 to 10.0 wt. %,

ii) melt flow index MFR ₂ determined in accordance with ISO 1133 (2.16 kg, 230°C) in the range from 4.0 to 20.0 g/10 min, and

iii) the amount of 2,1-erythro-regiodefects is at least 0.2 mol%.

In a preferred embodiment of the invention, a polypropylene composition (P) is provided, comprising at least 90.0 wt. %, based on the total weight of the polypropylene composition (P), copolymer (C) of propylene and 1-hexene, having

i) the total content of 1-hexene in the range from 2.0 to 10.0 wt. %,

ii) melt flow index MFR ₂ determined in accordance with ISO 1133 (2.16 kg, 230°C) in the range from 4.0 to 20.0 g/10 min, and

iii) an amount of 2,1-erythro-regiodefects of at least 0.2 mole %, wherein the copolymer (C) has been visbreaked with a visbreaking ratio (VR) in the range of 1.5 to 15.0, where the visbreaking is defined as according to equation (2)

,

,

in which "MFR _con " is the melt flow index MFR ₂ determined according to ISO 1133 (230° C., 2.16 kg), copolymer (C) after visbreaking, and " _MFR initial" is the melt flow index MFR2, determined in accordance with ISO 1133 (230°C, 2.16 kg), copolymer (C) before visbreaking.

According to one embodiment of the invention, the copolymer (C) has a xylene solubles (XCS) content of at least 8.0 wt. %.

According to another embodiment of the invention, the copolymer (C) comprises

a) the first random propylene copolymer (A) of propylene and 1-hexene, having a comonomer content in the range from 0.1 to 4.0 wt. %, and

b) a second random propylene copolymer (B) of propylene and 1-hexene having a higher comonomer content than the first random propylene copolymer (A).

In accordance with another embodiment of the invention, the copolymer (C) has a content of 1-hexene in the fraction of soluble substances in xylene C6 (XCS) in the range from 2.0 to 15.0 wt. %.

In accordance with another embodiment of the invention, the copolymer (C) comprises from 30.0 to 70.0 wt. % of the first random propylene copolymer (A) and from 30.0 to 70.0 wt. % of the second random propylene copolymer (B), based on the total weight of the copolymer (C).

In accordance with one embodiment of the invention, the copolymer (C) has a melting point Tm below 140°C.

In accordance with another embodiment of the invention, the copolymer (C) corresponds to equation (1)

,

,

where

C6(A) is the content of 1-hexene in the first random propylene copolymer (A) based on the total weight of the first random propylene copolymer (A) [in wt. %];

C6(C) is the content of 1-hexene in the copolymer (C) based on the total weight of the copolymer (C) [in wt. %]; and

[A]/[C] is the weight ratio between the first random propylene copolymer (A) and the copolymer (C) [in g/g].

In accordance with another embodiment of the invention, the copolymer (C) was subjected to visbreaking with a visbreaking ratio (VR) in the range from 1.5 to 15.0, where the visbreaking is determined in accordance with equation (2)

,

,

in which "MFR _con " is the melt flow rate MFR ₂ determined according to ISO 1133 (230° C., 2.16 kg), copolymer (C) after visbreaking, and "MFR _initial " is the melt flow rate MFR ₂ determined in accordance with ISO 1133 (230°C, 2.16 kg), copolymer (C) before visbreaking.

In accordance with one embodiment of the invention, the copolymer (C) has a melt flow index MFR ₂ determined in accordance with ISO 1133 (230°C, 2.16 kg), before visbreaking in the range from 0.4 to less than 4.0 g/10 min .

In accordance with another embodiment of the invention, the first random propylene copolymer (A) has an MFR of ₂ (230° C., 2.16 kg), determined in accordance with ISO 1133, before visbreaking in the range from 0.3 to 6.0 g/10 min, and/or the second random propylene copolymer (B) has an MFR of ₂ (230° C., 2.16 kg) determined in accordance with ISO 1133 before visbreaking in the range of 0.1 to 4, 0 g/10 min.

The invention also provides a process for producing a copolymer (C) of propylene and 1-hexene, comprising the steps

a) obtaining a copolymer (C) of propylene and 1-hexene, having a total content of 1-hexene in the range from 2.0 to 10.0 wt. %, in the presence of a metallocene catalyst (MS),

b) visbreaking the copolymer (C) obtained in step a) with a visbreaking ratio (VR) ranging from 1.5 to 15.0, thereby obtaining a copolymer (C), where the visbreaking is determined in accordance with equation (3 )

,

,

in which "MFR(C)" is the melt flow index MFR ₂ determined in accordance with ISO 1133 (230°C, 2.16 kg), copolymer (C) after visbreaking, and "MFR(C')" is melt flow index MFR ₂ determined in accordance with ISO 1133 (230°C, 2.16 kg), copolymer (C).

In accordance with one embodiment of the invention, the copolymer (C) of propylene and 1-hexene is obtained by

a1) polymerizing propylene and 1-hexene in the first reactor (R-1) in the presence of a metallocene catalyst (MC), thereby obtaining a first random propylene copolymer (A) having a content of 1-hexene in the range from 0.1 to 4, 0 wt. %, a2) moving said first random propylene copolymer (A) and unreacted comonomers from the first reactor (R-1) to the second reactor (R-2), and a3) polymerizing propylene and 1-hexene in said second reactor (R-2 ) and in the presence of said first random propylene copolymer (A) to obtain a second random propylene copolymer (B) having a higher 1-hexene content than the first random propylene copolymer (A), wherein said first random propylene copolymer (A) and said the second random propylene copolymer (B) form the copolymer (C). In accordance with another embodiment of the invention, the melt flow index MFR ₂ determined in accordance with ISO 1133 (230°C, 2.16 kg), copolymer (C) is in the range from 4.0 to 20.0 g/10 min, and the melt flow index MFR ₂ determined in accordance with ISO 1133 (230° C., 2.16 kg) of the copolymer (C) is in the range from 0.4 to less than 4.0 g/10 min.

In accordance with another embodiment of the invention, the metallocene catalyst (MC) has the formula (I)

,

,

where

each Cp is independently an unsubstituted or substituted and/or fused cyclopentadienyl ligand, a substituted or unsubstituted indenyl, or a substituted or unsubstituted fluorenyl ligand; wherein the possible one or more substituent(s) are independently selected preferably from halogen, hydrocarbyl (e.g. C1-C20 alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C3-C12 cycloalkyl, C6-C20 aryl or -C20-arylalkyl), C3-C12-cycloalkyl, which contains 1, 2, 3 or 4 heteroatoms (heteroatoms) in the ring group, C6-C20-heteroaryl, C1-C20-haloalkyl, -SiR'' ₃ , -OSiR'' ₃ , -SR'', -PR'' ₂ , -OR'' or -NR'' ₂ ,

each R'' is independently hydrogen or hydrocarbyl selected from C1-C20 alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C3-C12 cycloalkyl, or C6-C20 aryl; or in the case of -NR''2, two R'' substituents may form a spotted six-membered ring together with the nitrogen atom to which they are attached;

R is a bridge of 1-2 C atoms and 0-2 heteroatoms, in which the heteroatom(s) may be Si, Ge and/or O atom(s), where each of the bridge atoms may independently have substituents selected from substituents selected from C1-C20 alkyl, tri(C1-C20 alkyl)silyl, tri(C1-C20 alkyl)siloxy, or C6-C20 aryl; or a bridge of one or two heteroatoms selected from silicon, germanium and/or oxygen atom(s), M is a Group 4 transition metal selected from Zr or Hf, especially Zr;

each X is independently a sigma ligand selected from H, halogen, C1-C20 alkyl, C1-C20 alkoxy, C2-C20 alkenyl, C2-C20 alkynyl, C3-C12 cycloalkyl, C6-C20 aryl , C6-C20-aryloxy, C7-C20-arylalkyl, C7-C20-arylalkenyl, -SR'', -PR'' ₃ , -SiR'' ₃ , -OSiR'' ₃ , -NR'' ₂ or -CH ₂ -Y, where Y is C6-C20-aryl, C6-C20-heteroaryl, C1-C20-alkoxy, C6-C20-aryloxy, NR''2,-SR'', -PR'' ₃ , -SiR '' ₃ or -OSiR''₃;

each of the above ring moieties, alone or as part of another moiety as a substituent on Cp, X, R'' or R, may be further substituted with C1-C20 alkyl which may contain Si and/or O atoms; and n is 1 or 2.

Particularly preferably, the metallocene catalyst (MC) of formula (1) is an organozirconium compound of formula (II) or (II')

,

,

where

M is Zr;

each X is a sigma ligand, preferably each X is independently a hydrogen atom, a halogen atom, a C1-C6 alkoxy group, a C1-C6 alkyl, phenyl or benzyl group; L is a divalent bridge selected from -R' ₂ C-, -R' ₂ C-CR' ₂ , -R' ₂ Si-, -R' ₂ Si-SiR' ₂ -, -R' ₂ Ge-, where each R' independently represents a hydrogen atom, C1-C20 alkyl, C3-C10 cycloalkyl, tri(C1-C20-alkyl)silyl, C6-C20-aryl or C7-C20 arylalkyl;

each R ² or R ² is a C1-C10 alkyl group;

R ⁵ ' is a C1-C10 alkyl group or a Z'R ³ 'group;

R ⁶ is hydrogen or a C1-C10 alkyl group;

R ⁶ ' represents a C1-C10 alkyl group or a C6-C10 aryl group;

R ⁷ is hydrogen, a C1-C6 alkyl group or a ZR ³ group;

R ⁷ ' represents hydrogen or a C1-C10 alkyl group; Z and Z' are independently O or S;

R ³ ' represents a C1-C10 alkyl group, or a C6-C10 aryl group, optionally substituted with one or more halogen groups; R is a C1-C10 alkyl group; each n is independently 0 to 4;

and each R ¹ is independently a C1-C20 hydrocarbyl group.

The invention also provides a polypropylene composition (P) comprising at least 90.0 wt. % copolymer (C) obtained by the method described above.

The invention also provides an article comprising at least 90.0 wt. % of the above polypropylene composition (P).

Particularly preferably, the product is a film, more preferably a cast film.

The invention also proposes the use of the article described above as a sealing layer in a multilayer film.

Next, the polypropylene composition (P) is described in more detail.

Polypropylene composition (P) according to the invention includes at least 90.0 wt. %, based on the total weight of the polypropylene composition (P), copolymer (C) of propylene and 1-hexene.

Preferably, the polypropylene composition (P) includes at least 95.0 wt. % copolymer (C), more preferably at least 97.0 wt. %, even more preferably at least 98.0 wt. %, for example at least 99.0 wt. %, based on the total weight of the polypropylene composition (P). Particularly preferably, the polypropylene composition (P) consists of a copolymer (C).

The copolymer (C) according to the invention is characterized by a sufficiently high comonomer content, ie 1-hexene content. This sufficiently high comonomer content is achieved due to the fact that the copolymer (C) according to the invention comprises two propylene copolymer fractions as defined here. A "comonomer" according to the invention is a polymerizable molecule other than propylene. Accordingly, the copolymer (C) according to the invention should have a content of 1-hexene in the range from 2.0 to 10.0 wt. %, more preferably in the range from 3.0 to 8.0 wt. %, even more preferably in the range from 4.0 to 7.0 wt. %, for example, in the range from 3.0 to 8.0 wt. %.

In addition, the copolymer (C) according to the invention preferably has a melt flow index (MFR) in a certain range. The melt flow index, measured under a load of 2.16 kg at 230°C (ISO 1133), is designated MFR ₂ (230°C, 2.16 kg). Accordingly, the copolymer (C) according to the invention has a melt flow index MFR ₂ (230°C, 2.16 kg), determined according to ISO 1133, in the range from 4.0 to 20.0 g/10 min, preferably in the range from 5 0 to 15.0 g/10 min, more preferably in the range of 6.0 to 12.0 g/10 min, even more preferably in the range of 7.0 to 11.0 g/10 min.

As noted above, the polypropylene composition (P) must be particularly suitable for the production of packaging. Accordingly, good sealing properties are required, such as a sufficiently low heat seal start temperature (HST) and a wide seal window combined with low tack.

Accordingly, the polypropylene composition (P) preferably has a heat seal start temperature (HST) equal to or lower than 117°C, more preferably equal to or lower than 113°C, even more preferably in the range from 93 to equal to or lower than 113°C, and still more preferably in the range of 93 to equal to or less than 110°C.

In addition, not only the heat seal start temperature (HST) must be sufficiently low, but also the melting point (Tm) must be sufficiently high. Accordingly, the difference between the melting point (Tmelt) and the heat sealing start temperature (TNG) must be sufficiently high. Thus, the polypropylene composition (P) preferably corresponds to equation (3), more preferably equation (3a), even more preferably equation (3b)

,

,

where

Tm - melting temperature in degrees Celsius [°C] of the polypropylene composition (P),

TNG - the temperature of the beginning of thermal sealing in degrees Celsius [°C] of the polypropylene composition (P).

The melting point (Tm), measured according to ISO 11357-3, of the copolymer (C) is preferably below 140°C. Thus, in particular, it is understood that the melting point (M) measured according to ISO 11357-3 of the copolymer (C) is in the range from 125 to less than 140°C, more preferably in the range from 125 to less than 140°C, still more preferably in the range from 128 to 139°C.

In addition, the copolymer (C) may have xylene cold solubles (XCS) measured according to ISO 16152 (25°C). Accordingly, the copolymer (C) preferably has a cold xylene solubles (XCS) content of at least 8.0 wt. %, more preferably in the range from 8.0 to 20.0 wt. %, even more preferably in the range from 9.0 to 18.0 wt. %, for example, in the range from 9.0 to 15.0 wt. %.

This cold xylene solubles (XCS) content also indicates that the copolymer (C) preferably does not contain any elastomeric polymer component such as ethylene-propylene rubber. In other words, the copolymer (C) should not be a heterophasic polypropylene, that is, a system consisting of a polypropylene matrix in which the elastomeric phase is dispersed. Such systems are characterized by a rather high content of substances soluble in cold xylene. Accordingly, in a preferred embodiment, the copolymer (C) comprises the first random propylene copolymer (A) and the second random propylene copolymer (B) as the sole polymer components.

In addition, the copolymer (C) preferably has a content of 1-hexene in the xylene-soluble fraction, C6(XCS), in the range from 2.0 to 15.0 wt. %, more preferably in the range from 3.5 to 12.0 wt. %, even more preferably in the range from 4.0 to 10.0 wt. %, for example, in the range from 5.0 to 8.0 wt. %.

Similar to cold xylene solubles (XCS), hot hexane solubles (HHS) indicate the portion of the polymer that has low isotacticity and crystallinity and is hexane soluble at 50°C.

Accordingly, preferably, the copolymer (C) according to the invention has a content of substances soluble in hot hexane (HHS), measured in accordance with FDA 177.1520, equal to or less than 1.5 wt. %, more preferably equal to or less than 1.0 wt. %, even more preferably equal to or less than 0.8 wt. %.

The copolymer (C) has a content of 2,1-erythro-regiodefects of at least 0.2 mol.%, preferably at least 0.3 mol.%, even more preferably at least 0.4 mol.%. Without being bound by theory, a large number of incorrect incorporations of propylene and/or 1-hexene in the polymer chain indicates that the copolymer (C) was obtained in the presence of a single site th (with the same active sites) catalyst, preferably a metallocene catalyst.

According to a preferred embodiment of the present invention, the copolymer (C) has been visbroken.

The visbreaked copolymer (C) has a higher melt flow index than the non-visbroken copolymer (C).

Accordingly, the copolymer (C) preferably has a melt flow index MFR ₂ (230°C, 2.16 kg), determined in accordance with ISO 1133, before visbreaking in the range from 0.4 to less than 4.0 g/10 min, more preferably in the range of 0.6 to 3.5 g/10 min, even more preferably in the range of 0.8 to 3.0 g/10 min, e.g. in the range of 1.3 to 2.0 g/10 min .

In one embodiment of the invention, the copolymer (C) has been visbreaked with a visbreaking ratio (VR) ranging from 1.5 to 15.0, where the visbreaking is determined in accordance with equation (2)

,

,

where "PT _con " is the melt flow index MFR ₂ determined in accordance with ISO 1133 (230°C, 2.16 kg), copolymer (C) after visbreaking, and " _MFR in" is the melt flow index MFR ₂ , determined in accordance with ISO 1133 (230°C, 2.16 kg), copolymer (C) before visbreaking. More preferably, said visbreaking ratio (VR) is in the range of 2.0 to 12.0, such as in the range of 3.0 to 10.0.

Preferred mixers suitable for visbreaking are batch and continuous mixers, twin screw extruders and single screw extruders with dedicated mixing sections and co-mixers.

By visbreaking the copolymer (C) under heating or under more controlled conditions in the presence of visbreaking agents such as peroxides, the molecular weight distribution (MWD) becomes narrower as long molecular chains are more easily broken or cleaved and the molecular weight M is reduced, which corresponds to an increase in MFR ₂ . MFI ₂ increases with the amount of visbreaking agent used.

Unless otherwise indicated, the melt flow rates given herein are the melt flow rates after visbreaking.

Such visbreaking can be carried out by any known method, for example with a peroxide visbreaking agent. Typical visbreaking agents are 2,5-dimethyl-2,5-bis(tert-butyl-peroxy)hexane (DHBP) (e.g. sold under the tradenames Luperox 101 and Trigonox 101), 2,5-dimethyl-2,5- bis(tert-butyl-peroxy)hexine-3 (DYBP) (eg sold under the trade names Luperox 130 and Trigonox 145), dicumyl peroxide (DCUP) (eg sold under the trade names Luperox DC and Perkadox BC), di-tert- butyl peroxide (DTBP) (for example, sold under the trade names Trigonox B and Luperox Di), tert-butyl cumyl peroxide (BCUP) (for example, sold under the trade names Trigonox T and Luperox 801), and bis(tert-butylperoxyisopropyl)benzene (DIPP) (for example, sold under the trade names Perkadox 14S and Luperox DC). The appropriate amount of peroxide to be used in accordance with the invention is in principle known to the skilled person and can be easily calculated based on the amount of copolymer (C) subjected to visbreaking, an MFR value of ₂ (230° C./2.16 kg) of copolymer (C), subjected to visbreaking, and the desired target MFR ₂ (230°C/2.16 kg) of the product to be obtained. Accordingly, typical amounts of peroxide visbreaking agent are from 0.005 to 0.7 wt. %, preferably from 0.01 to 0.4 wt. %, based on the total amount of copolymer (C) used.

As a rule, visbreaking according to the invention is carried out in an extruder, so that, under suitable conditions, an increase in the melt flow index is achieved. During visbreaking, chains with higher molecular weight starting material are statistically broken more frequently than molecules with lower molecular weight, resulting, as shown above, in an overall decrease in average molecular weight and an increase in melt flow index.

The copolymer (C) according to the invention is further characterized by the polymer fractions present therein. According to a preferred embodiment of the invention, the copolymer (C) is at least bimodal. Accordingly, the copolymer (C) according to the invention preferably comprises at least, more preferably consists of two fractions, namely the first random propylene copolymer (A) and the second random propylene copolymer (B). The copolymer (C) includes a first random propylene copolymer (A) and a second random propylene copolymer (B). The term "random copolymer" should preferably be understood in accordance with IUPAC (Pure Appl. Chem., Vol. No. 68, 8, pp. 1591-1595, 1996). Preferably, the molar concentration of comonomeric dyads, such as 1-hexene dyads, corresponds to the ratio

[НН]<[Н] ² ,

where

[HH] is the mole fraction of contiguous comonomer units, in particular contiguous 1-hexene units, and

[H] the mole fraction of the total comonomer units, in particular the total number of 1-hexene units, in the polymer.

The first random propylene copolymer (A) is a propylene-1-hexene copolymer having a 1-hexene content in the range of 0.1 to 4.0 wt. %, preferably in the range from 0.5 to 3.5 wt. %, more preferably in the range from 0.8 to 3.0 wt. %, even more preferably in the range from 1.0 to 2.5 wt. %, and the second random propylene copolymer (B) is a copolymer of propylene and 1-hexene, having a higher content of 1-hexene than the first random copolymer (A), preferably in the range from 4.0 to 20.0 wt. %, more preferably in the range from 5.0 to 15.0 wt. %, even more preferably in the range from 6.0 to 12.0 wt. %, and even more preferably in the range from 6.5 to 10.0 wt. %.

Accordingly, the first random propylene copolymer (A) is a fraction poor in 1-hexene, while the second random propylene copolymer (B) is a fraction rich in 1-hexene.

In addition, it should be understood that the first random propylene copolymer (A) has an MFR of ₂ (230°C, 2.16 kg), determined in accordance with ISO 1133, before visbreaking in the range from 0.3 to 6.0 g/10 min, more preferably in the range of 0.5 to 5.0 g/10 min, even more preferably in the range of 0.8 to 3.0 g/10 min.

The second propylene copolymer (B) preferably has an MFR of ₂ (230° C., 2.16 kg) determined according to ISO 1133 before visbreaking in the range of 0.1 to 4.0 g/10 min, more preferably in the range of 0.3 to 3.5 g/10 min, even more preferably in the range of 0.6 to 2.5 g/10 min, for example in the range of 0.9 to 2.0 g/10 min.

Preferably, the weight ratio between the first random propylene copolymer (A) and the second random propylene copolymer (B) in the copolymer (C) is in the range of 30:70 to 70:30, more preferably in the range of 35:65 to 65:35, still more preferably in the range of 40:60 to 60:40.

In particular, it is preferred that the copolymer (C) comprises from 30.0 to 70.0 wt. %, more preferably from 35.0 to 50.0 wt. %, even more preferably from 38.0 to 45.0 wt. %, for example from 39.0 wt. % to 43.0 wt. % of the first random propylene copolymer (A) and from 30.0 to 70.0 wt. %, more preferably from 40.0 to 65.0 wt. %, even more preferably from 48.0 to 60.0 wt. %, for example from 52.0 to 55.0 wt. % of the second random propylene copolymer (B), based on the total weight of the copolymer (C).

In addition, the copolymer (C) may contain additives (AD).

Accordingly, preferably, the copolymer (C) comprises, more preferably consists of, from 20.0 to 55.0 wt. %, more preferably from 35.0 to 50.0 wt. %, even more preferably 38.0 to 45.0 wt. %, for example from 40.0 wt. % to 43.0 wt. % of the first random propylene copolymer (A) and from 45.0 to 80.0 wt. %, more preferably from 50.0 to 65.0 wt. %, even more preferably from 55.0 to 62.0 wt. %, for example from 57.0 to 60.0 wt. % of the second random propylene copolymer (B), as well as from 0.01 to 5.0 wt. %, more preferably from 0.03 to 3.0 wt. %, even more preferably from 0.06 to 2.0 wt. %, for example from 0.08 to 1.0 wt. % additives (AD), based on the total weight of the copolymer (C).

Typical additives are acid scavengers, antioxidants, colorants, light stabilizers, plasticizers, lubricants, anti-scratch agents, dispersants, processing aids, lubricants, pigments, and the like.

Such additives are commercially available and are, for example, described in "Plastic Additives Handbook", 6th ^edition 2009 of Hans Zweifel (pages 1141 to 1190). (“Handbook of plastic additives”, 6th edition, 2009, Hans Zweifel, pp. 1141 - 1190).

In addition, the term "additives (AD)" in accordance with the invention also includes carrier materials, in particular polymeric carrier materials.

Polymer carrier material

Preferably, the copolymer (C) according to the invention does not contain additional polymer(s) other than the first random propylene copolymer (A) and the second random propylene copolymer (B) in an amount exceeding 15 wt. %, preferably in an amount exceeding 10 wt. %, more preferably in an amount greater than 9 wt. %, based on the weight of the copolymer (C). Any polymer that is an additive carrier material (AD) is not calculated on the amount of polymer compounds as specified in the invention, but on the amount of the respective additive.

The additive carrier polymeric material (AD) is a carrier polymer to ensure uniform distribution in the copolymer (C) according to the invention. The polymeric carrier material is not limited to a particular polymer.

The polymeric carrier material may be an ethylene homopolymer, an ethylene copolymer derived from ethylene and an α-olefin comonomer such as a C3-C8 α-olefin comonomer, a propylene homopolymer and/or a propylene copolymer derived from propylene and an α-olefin comonomer such as ethylene and/or C4-C8 α-olefin comonomer. Preferably, the carrier polymeric material does not contain monomeric units derived from styrene or its derivatives. It is particularly preferred that the polymeric material of the carrier is polypropylene.

The copolymer (C) was obtained by the method defined in detail below.

The method for producing a copolymer (C) of propylene and 1-hexene includes the steps

a) obtaining a copolymer (C) of propylene and 1-hexene, having a total content of 1-hexene in the range from 2.0 to 10.0 wt. %, in the presence of a metallocene catalyst (MS),

b) visbreaking the copolymer (C) obtained in step a), with a visbreaking ratio (VR) in the range of 1.5 to 15.0, to obtain a copolymer (C), where the visbreaking is determined in accordance with equation (3)

,

,

in which "MFR(C)" is the melt flow index MFR ₂ determined in accordance with ISO 1133 (230°C, 2.16 kg), copolymer (C) after visbreaking, and "MFR(C')" is melt flow index MFR ₂ determined in accordance with ISO 1133 (230°C, 2.16 kg), copolymer (C).

The copolymer (C) according to step a) corresponds to the copolymer (C) before visbreaking. As mentioned above, the molecular weight of the propylene copolymer decreases during the visbreaking process, whereby the melt flow index increases. However, outside of theory, the visbreaking process does not affect the comonomer content, tacticity, and cold xylene solubles content of the propylene copolymer. Thus, the above ranges of 1-hexene, cold xylene solubles (XCS) and hot hexane solubles (HHS) of the copolymer (C) apply, respectively, to the copolymer (C).

Thus, the copolymer (C) has a content of 1-hexene in the range from 2.0 to 10.0 wt. %, preferably in the range from 3.0 to 8.0 wt. %, for example, in the range from 4.0 to 7.0 wt. %.

In addition, the copolymer (C) can be characterized by cold xylene solubles (XCS) measured according to ISO 16152 (25°C). Accordingly, the copolymer (C) preferably has a cold xylene solubles (XCS) content of at least 8.0 wt. %, more preferably in the range from 8.0 to 20.0 wt. %, even more preferably in the range from 9.0 to 18.0 wt. %, for example in the range from 9.0 to 15.0 wt. %.

In addition, preferably, the copolymer (C) according to the invention has a content of hot hexane soluble substances (HHS), measured in accordance with FDA 177.1520, equal to or less than 1.5 wt. %, more preferably equal to or less than 1.0 wt. %, even more preferably equal to or less than 0.8 wt. %.

The copolymer (C) preferably has a melt flow index MFR ₂ (230°C, 2.16 kg), determined in accordance with ISO 1133, in the range from 0.4 to less than 4.0 g/10 min, more preferably in the range from 0.6 to 3.5 g/10 min, even more preferably in the range of 0.8 to 3.0 g/10 min, for example in the range of 1.0 to 2.0 g/10 min.

The copolymer (C) according to the invention is further characterized by the polymer fractions present therein. According to a preferred embodiment of the invention, the copolymer (C) is at least bimodal. Accordingly, the copolymer (C) according to the invention preferably comprises at least, more preferably consists of two fractions, namely the first random propylene copolymer (A) and the second random propylene copolymer (B).

Accordingly, the copolymer (C) according to step a) of the process according to the invention is preferably obtained by

a1) polymerizing propylene and 1-hexene in the first reactor (R-1) in the presence of a metallocene catalyst (MC), thereby obtaining a first random propylene copolymer (A) having a content of 1-hexene in the range from 0.1 to 4, 0 wt. %, a2) moving said first random propylene copolymer (A) and unreacted comonomers from the first reactor (R-1) to the second reactor (R-2), and a3) polymerizing propylene and 1-hexene in said second reactor (R-2 ) and in the presence of said first random propylene copolymer (A) to obtain a second random propylene copolymer (B) having a higher 1-hexene content than the first random propylene copolymer (A), wherein said first random propylene copolymer (A) and said the second random propylene copolymer (B) form the copolymer (C). The first random propylene copolymer (A) is a propylene-1-hexene copolymer, preferably having a 1-hexene content in the range of 0.1 to 4.0 wt. %, more preferably in the range from 0.5 to 3.5 wt. %, even more preferably in the range from 0.8 to 3.0 wt. %, and even more preferably in the range from 1.0 to 2.5 wt. %, and the second random propylene copolymer (B) is a copolymer of propylene and 1-hexene having a higher content of 1-hexene than the first random copolymer (A), preferably in the range from 4.0 to 20.0 wt. %, more preferably in the range from 5.0 to 15.0 wt. %, even more preferably in the range from 6.0 to 12.0 wt. %, and even more preferably in the range from 6.5 to 10.0 wt. %.

Accordingly, preferably, the first random propylene copolymer (A) is a fraction poor in 1-hexene, while the second random propylene copolymer (B) is a fraction rich in 1-hexene. In other words, the second random propylene copolymer (B) preferably has a higher comonomer content than the propylene copolymer (A).

In addition, it should be understood that the first random propylene copolymer (A) has an MFR of ₂ (230°C, 2.16 kg), determined in accordance with ISO 1133, before visbreaking in the range from 0.3 to 6.0 g/10 min, more preferably in the range of 0.5 to 5.0 g/10 min, even more preferably in the range of 0.8 to 3.0 g/10 min.

The second propylene copolymer (B) preferably has an MFR of ₂ (230° C., 2.16 kg) determined according to ISO 1133 before visbreaking in the range of 0.1 to 4.0 g/10 min, more preferably in the range of 0.3 to 3.5 g/10 min, even more preferably in the range of 0.6 to 2.5 g/10 min, for example in the range of 0.9 to 1.3 g/10 min.

In step b) of the method according to the invention, the copolymer (C) is subjected to visbreaking to obtain the copolymer (C). With regard to the preferred visbreaking method, reference may be made to the above definitions.

Copolymer (C) is subjected to visbreaking with a visbreaking ratio (VR) ranging from 1.5 to 15.0 to obtain copolymer (C), where visbreaking is determined in accordance with equation (3)

,

,

in which "MFR(C)" is the melt flow index MFR ₂ determined in accordance with ISO 1133 (230°C, 2.16 kg), copolymer (C) after visbreaking, and "MFR(C')" is melt flow index MFR ₂ determined in accordance with ISO 1133 (230°C, 2.16 kg), copolymer (C). More preferably said visbreaking ratio (VR) is in the range of 2.0 to 12.0, for example in the range of 3.0 to 10.0.

Preferably, the melt flow index MFR ₂ determined in accordance with ISO 1133 (230° C., 2.16 kg) of the copolymer (C), i.e. the melt flow index MFR ₂ after visbreaking, is in the range from 4.0 to 20.0 g/10 min, more preferably in the range of 5.0 to 15.0 g/10 min, even more preferably in the range of 6.0 to 12.0 g/10 min, and even more preferably in the range of 7.0 up to 11.0 g/10 min, and the melt flow index MFR ₂ determined in accordance with ISO 1133 (230°C, 2.16 kg), copolymer (C), i.e. the melt flow index MFR ₂ before visbreaking, is in in the range of 0.4 to less than 4.0 g/10 min, more preferably in the range of 0.6 to 3.5 g/10 min, even more preferably in the range of 0.8 to 3.0 g/10 min, for example, in the range from 1.0 to 2.5 g/10 min.

Further preferably, the metallocene catalyst (MC) is a transition metal compound of formula (I) as defined in more detail below.

A method for producing a copolymer (C) forming a polypropylene composition (P) as described above is a sequential polymerization method comprising at least two reactors connected in series, wherein said method includes the steps

(A) polymerizing in the first reactor (R-1), which is a slurry reactor (SR), preferably a loop reactor (LR), propylene and 1-hexene, to obtain the first random propylene copolymer (A),

(B) transferring said first random propylene copolymer (A) and unreacted comonomers from the first reactor (R-1) to the second reactor (R-2), which is a gas phase reactor (GPR-1),

(C) feeding said second reactor (R-2) propylene and 1-hexene,

(D) polymerizing propylene and 1-hexene in said second reactor (R-2) and in the presence of said first random propylene copolymer (A) to obtain a second random propylene copolymer (B), thereby obtaining a composition (C) comprising a first random a propylene copolymer (A) and a second random propylene copolymer (B), and

(E) extruding the composition (C') comprising the first random propylene copolymer (A) and the second random propylene copolymer (B) obtained in step (D) and in the presence of a visbreaking agent, preferably a peroxide, thereby obtaining a copolymer (C) polypropylene composition (P),

in which also

in the first reactor (R-1) and the second reactor (R-2) the polymerization takes place in the presence of a metallocene catalyst (MC) comprising (i) a transition metal compound of formula (I)

,

,

where

"M" represents zirconium (Zr) or hafnium (Hf),

each "X" is independently a monovalent anionic σ-ligand, each "Cp" is a cyclopentadienyl-type organic ligand independently selected from the group consisting of unsubstituted or substituted and/or fused cyclopentadienyl, substituted or unsubstituted indenyl, or substituted or unsubstituted fluorenyl, moreover, these organic ligands are coordinated with the transition metal (M),

"R" is a divalent bridging group connecting said organic ligands (Cp), "n" is 1 or 2, preferably 1, and

(ii) optionally, a cocatalyst (Co) comprising an element (E) of group 13 of the Periodic Table (IUPAC), preferably a cocatalyst (Co) comprising compound A1 and/or B.

With regard to the definition of the copolymer (C), the first random propylene copolymer (A) and the second random propylene copolymer (B), refer to the definitions above.

The metallocene catalyst (MC) is defined in more detail below.

By using a metallocene catalyst (MC) in the sequential polymerization process, the aforementioned copolymer (C) can be obtained. In particular, by producing the propylene copolymer, i.e. the first random propylene copolymer (A), in the first reactor (R-1) and transferring said propylene copolymer and especially transferring unreacted comonomers to the second reactor (R-2), it is possible to obtain copolymer (C) with a high comonomer content in a sequential polymerization process. Typically, the production of a high comonomer propylene copolymer in a sequential polymerization process results in fouling or, in severe cases, plugging of the transfer lines, as normally unreacted comonomers condense in the transfer lines. However, in the new process, comonomer conversion is increased while achieving improved incorporation into the polymer chain, resulting in higher comonomer content and reduced stickiness problems.

The term "sequential polymerization process" indicates that the copolymer (C) is produced in at least two reactors connected in series. More precisely, the term "sequential polymerization process" indicates in this specification that the polymer from the first reactor (R-1) is directly transferred along with the unreacted comonomers to the second reactor (R-2). Accordingly, a crucial aspect of the proposed process is the preparation of the copolymer (C) in two different reactors, wherein the reaction material of the first reactor (R-1) is directly transferred to the second reactor (R-2). Thus, the proposed method includes at least a first reactor (R-1) and a second reactor (R-2). In one specific embodiment, the proposed method is to use two polymerization reactors (R-1) and (R-2). The term "polymerization reactor" should indicate that the main polymerization takes place in it. Thus, if the process consists of using two 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 a restrictive (restrictive) wording in relation to the main polymerization reactors.

The first reactor (R-1) is a slurry reactor (SR) and can be any continuous reactor or a simple stirred volume reactor or a slurry loop reactor. According to the invention, the slurry reactor (SR) is preferably a loop reactor (LR).

The second reactor (R-2) and any subsequent reactor are gas phase reactors (GPRs). Such gas phase reactors (GPRs) may be any mechanically agitated or fluidized bed reactors. Preferably gas phase reactors (GPRs) comprise a mechanically agitated fluidized bed reactor with a gas velocity of at least 0.2 m/s. Thus, it should be understood that the gas phase reactor is of the fluidized bed type, preferably mechanically agitated.

The conditions (temperature, pressure, reaction time, monomer feed) in each reactor depend on the desired product, which is within the skill of the art. As already mentioned above, the first reactor (R-1) is preferably a slurry reactor (SR) such as a loop reactor (LR), while the second reactor (R-2) is preferably a gas phase reactor (GPR-1). Subsequent reactors, if any, are also gas phase reactors (GPRs).

A preferred multi-stage process is a loop reactor-gas phase reactor process such as that developed by Borealis A/S, Denmark (known as the BORSTAR® technology) described for example in patent literature such as EP 0887379 or WO 92/12182 .

Multimodal polymers can be obtained in accordance with several processes, which are described, for example, in WO 92/12182, EP 0887379 and WO 98/58976. The contents of these documents are incorporated into this specification by reference.

Preferably, in the proposed process for producing the copolymer (C) as defined above, the conditions in the first reactor (R-1), i.e. the slurry reactor (SR) such as the loop reactor (LR), in step (A) may be as follows :

- the temperature is in the range from 40°C to 110°C, preferably from 60°C to 100°C, more preferably in the range from 65 to 90°C,

- the pressure is in the range of 20 bar to 80 bar (2 to 8 MPa), preferably 40 bar to 70 bar (4 to 7 MPa),

- hydrogen can be added to adjust the molar mass in a manner known per se.

Then the reaction mixture from stage (A) is transferred to the second reactor (R-2), i.e. to the gas phase reactor (GPR-1), i.e. to stage (D), while the conditions in stage (D) are preferably as follows:

- the temperature is in the range from 50°C to 130°C, preferably from 60°C to 100°C,

- the pressure is in the range of 5 bar to 50 bar (0.5 to 5 MPa), preferably 15 bar to 40 bar (1.5 to 4 MPa),

- hydrogen can be added to adjust the molar mass in a manner known per se.

The residence time in both reaction zones can be varied.

In one of the embodiments of the method for producing copolymer (C), the residence time in the slurry reactor (SR), for example, in the loop reactor (LR) is in the range from 0.2 to 4.0 hours, for example, from 0.3 to 1.5 hours, and the residence time in the gas phase reactor (GPR) is generally from 0.2 to 6.0 hours, for example from 0.5 to 4.0 hours.

If necessary, the polymerization can be carried out in a known manner under supercritical conditions in the first reactor (R-1), i.e. in a slurry reactor (SR), for example in a loop reactor (LR) and/or in condensed mode in a gas phase reactor (GPR-1) .

Conditions in other gas phase reactors (GPR), if any, are similar to the second reactor (R-2).

The proposed method may also include prepolymerization prior to polymerization in the first reactor (R-1). The prepolymerization can be carried out in the first reactor (R-1), however it is preferred that the prepolymerization takes place in a separate reactor, the so-called prepolymerization reactor.

The copolymer (C) according to the invention is preferably prepared in the presence of a metallocene catalyst (MC) comprising a transition metal compound.

In a preferred embodiment, the compound has a transition metal of formula (I)

,

,

where

each Cp is independently an unsubstituted or substituted and/or fused cyclopentadienyl ligand, for example a substituted or unsubstituted indenyl or a substituted or unsubstituted fluorenyl ligand; wherein the possible one or more substituent(s) are independently selected preferably from halogen, hydrocarbyl (e.g. C1-C20 alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C3-C12 cycloalkyl, C6-C20 aryl or -C20-arylalkyl), C3-C12-cycloalkyl, which contains 1, 2, 3 or 4 heteroatoms (heteroatoms) in the ring group, C6-C20-heteroaryl, C1-C20-haloalkyl, -SiR'' ₃ , -OSiR'' ₃ , -SR'', -PR'' ₂ , -OR'' or -NR'' ₂ ,

each R'' is independently hydrogen or hydrocarbyl, for example C1-C20 alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C3-C12 cycloalkyl, or C6-C20 aryl; or in the case of -NR'' ₂ , the two R'' substituents may form a five- or six-membered ring together with the nitrogen atom to which they are attached; R represents a bridge of 1-3 atoms, for example a bridge of 1-2 C atoms and 0-2 heteroatoms, in which the heteroatom(s) may be a Si, Ge and/or O atom(s), where each of the bridge atoms may independently have substituents selected from substituents such as C1-C20 alkyl, tri(C1-C20 alkyl)silyl, tri(C1-C20 alkyl)siloxy, or C6-C20 aryl; or a bridge of 1-3, for example, one or two heteroatoms, such as atom(s) of silicon, germanium and/or oxygen, for example, -SiR ¹⁰ ₂ where each R ¹⁰ is independently C1-C20-alkyl, C3- a 12-cycloalkyl, C6-C20-aryl or tri(C1-C20-alkyl)silyl moiety such as trimethylsilyl;

M is a Group 4 transition metal, for example Zr or Hf, especially Zr;

each X is independently a sigma ligand such as H, halogen, C1-C20 alkyl, C1-C20 alkoxy, C2-C20 alkenyl, C2-C20 alkynyl, C3-C12 cycloalkyl, C6-C20 aryl , C6-C20-aryloxy, C7-C20-arylalkyl, C7-C20-arylalkenyl, -SR'', -PR'' ₃ , -SiR'' ₃ , -OSiR'' ₃ , -NR'' ₂ or -CH ₂ -Y, where Y is C6-C20-aryl, C6-C20-heteroaryl, C1-C20-alkoxy, C6-C20-aryloxy, -NR'' ₂ , -SR'', -PR'' ₃ , - SiR'' ₃ or -OSiR''₃;

each of the above ring moieties, alone or as part of another moiety as a substituent on Cp, X, R'' or R, may be further substituted, for example with C1-C20 alkyl which may contain Si and/or O atoms; and

n is 1 or 2.

Accordingly, in each X representing -CH ₂ -Y, each Y is independently selected from C6-C20-aryl, -NR'' ₂ , -SiR'' ₃ or -OSiR'' ₃ . Most preferably, X representing -CH ₂ -Y is benzyl. Each X other than -CH ₂ -Y is independently halo, C1-C20 alkyl, C1-C20 alkoxy, C6-C20 aryl, C7-C20 arylalkenyl, or -NR'' ₂ as defined above, e.g. -N(C1-C20-alkyl) ₂ .

Preferably, each X is halogen, methyl, phenyl, or —CH ₂ —Y, and each Y is independently as defined above.

Cp is preferably cyclopentadienyl, indenyl or fluorenyl, optionally substituted as defined above. Ideally Cp is cyclopentadienyl or indenyl.

In a suitable subgroup of compounds of formula (I), each Cp independently has 1, 2, 3 or 4 substituents as above, preferably 1, 2 or 3, for example 1 or 2 substituents, which are preferably selected from C1-C20-alkyl, C6- C20-aryl, C7-C20-arylalkyl (in which the aryl ring alone or as part of another moiety may be further substituted as above), -OSiR'' ₃ in which R'' is as above, preferably C1 -C20-alkyl.

R is preferably a methylene, ethylene or silyl bridge, where the silyl may be substituted as defined above, eg (dimethyl)Si=, (methylphenyl)Si=, (methylcyclohexyl)silyl= or (trimethylsilylmethyl)Si=; n is 0 or 1. Preferably, R'' is other than hydrogen.

A particular subgroup includes the well-known Zr and Hf metallocenes with two eta5 ligands which are bridged with cyclopentadienyl ligands, optionally substituted with e.g. ligands optionally substituted on any of the ring moieties, eg siloxy or alkyl as defined above, eg 2-, 3-, 4- and/or 7-position. Preferred bridges are ethylene or -SiMe ₂ .

The preparation of metallocenes can be carried out according to or similar to methods known in the literature and within the skill of the art. Thus, with regard to preparation, see, for example, EP-A-129368, for examples of compounds in which the metal atom has a -NR'' ₂ ligand, see in particular WO-A-9856831 and WO-A-0034341. With regard to preparation, see also, for example, EP-A-260130, WO-A-9728170, WO-A-9846616, WO-A-9849208, WO-A-9912981, WO-A-9919335, WO-A-9856831 , WO-A-0034341, EP-A-423101 and EP-A-537130.

The complexes according to the invention are preferably asymmetric. This simply means that the two indenyl ligands forming the metallocene are different, that is, each indenyl ligand has a set of substituents that are either chemically different or located at different positions relative to the other indenyl ligand. More precisely, these complexes are chiral, racemic bridged bis-indenyl metallocenes. While the complexes of the invention may ideally be in their syn configuration, they are in the anti configuration. In relation to this invention, "racemic-anti" means that the two indenyl ligands are oriented in opposite directions with respect to the cyclopentadienyl-metal-cyclopentadienyl plane, while "racemic-syn" means that the two indenyl ligands are oriented in the same direction along with respect to the cyclopentadienyl-metal-cyclopentadienyl plane.

Preferred complexes of the invention have the formula (II') or (II)

,

,

where

M is Zr;

each X is a sigma ligand, preferably each X is independently a hydrogen atom, a halogen atom, a C1-C6 alkoxy group, a C1-C6 alkyl, phenyl or benzyl group; L is a divalent bridge selected from -R' ₂ C-, -R' ₂ C-CR' ₂ , -R' ₂ Si-, -R' ₂ Si-SiR' ₂ , -R' ₂ Ge-, where each R' independently represents a hydrogen atom, C1-C20 alkyl, C3-C10 cycloalkyl, tri(C1-C20-alkyl)silyl, C6-C20-aryl or C7-C20 arylalkyl;

each R ² or R ² ' represents a C1-C10 alkyl group;

R ⁵ ' is a C1-C10 alkyl group or a Z'R ³ 'group;

R ⁶ is hydrogen or a C1-C10 alkyl group;

R ⁶ ' represents a C1-C10 alkyl group or a C6-C10 aryl group;

R ⁷ is hydrogen, a C1-C6 alkyl group or a ZR ³ group;

R ⁷ ' represents hydrogen or a C1-C10 alkyl group; Z and Z' are independently O or S;

R ³ ' represents a C1-C10 alkyl group, or a C6-C10 aryl group, optionally substituted with one or more halogen groups;

R ³ is a C1-C10 alkyl group;

each n is independently 0 to 4, such as 0.1 or 2;

and each R ¹ is independently a C1-C20 hydrocarbyl group, for example a C1-C10 alkyl group.

Particularly preferred compounds according to the invention include: rac-dimethylsilandiylbis[2-methyl-4-(4-tert-butylphenyl)-1,5,6,7-tetrahydro-S-indacen-1-yl]-zirconium dichloride

rac-dimethylsilandiylbis(2-methyl-4-phenyl-5-methoxy-6-tert-butylinden-1-yl)-zirconium dichloride

rac-anti-Me ₂ Si(2-Me-4-Ph-6-tBu-Ind)(2-Me-4-Ph-5-OMe-6-tBu-Ind)ZrCl ₂

rac-anti-Me ₂ Si(2-Me-4-(p-tBuPrl)-Ind)(2-Me-4-Ph-5-OMe-6-tBu-Ind)ZrCl ₂

rac-anti-Me ₂ Si(2-Me-4-(3,5-di-tBuPrl)-6-tBu-Ind)(2-Me-4-Ph-5-OMe-6-tBu-Ind)ZrCl ₂

rac-anti-Me ₂ Si(2-Me-4-(p-tBuPrl)-Ind)(2-Me-4-Ph-5-OC ₆ F ₅ )-6-iPr-Ind)ZrCl ₂

rac-anti-Me(CyHex)Si(2-Me-4-Ph-6-tBu-Ind)(2-Me-4-Ph-5-OMe-6-tBu-Ind)ZrCl ₂

rac-anti-Me ₂ Si(2-Me-4-(3,5-di-BuPh)-7-Me-Ind)(2-Me-4-Ph-5-OMe-6-tBu-Ind)ZrCl ₂

rac-anti-Me ₂ Si(2-Me-4-(3,5-di-tBuPh)-7-OMe-Ind)(2-Me-4-Ph-5-OMe-6-tBu-Ind)ZrCl ₂

rac-anti-Me ₂ Si(2-Me-4-(p-tBuPrl)-6-tBu-Ind)(2-Me-4-Ph-5-OMe-6-tBu-Ind)ZrCl ₂

rac-anti-Me ₂ Si(2-Me-4-(p-tBuPrl)-Ind)(2-Me-4-(4-tBuPh)-5-OMe-6-tBu-Ind)ZrCl ₂

rac-anti-Me ₂ Si(2-Me-4-(p-tBuPh)-Ind)(2-Me-4-(3.5-tBu2Ph)-5-OMe-6-tBu-Ind)ZrCl ₂

rac-anti-Me ₂ Si(2-Me-4-(p-tBuPrl)-Ind)(2-Me-4-Ph-5-OtBu-6-tBu-Ind)ZrCl ₂ .

The most preferred metallocene complex (procatalyst) is rac-anti-dimethylsilandiyl(2-methyl-4-phenyl-5-methoxy-6-tert-butyl-indenyl)(2-methyl-4-(4-tert-butylphenyl)indenyl) zirconium dichloride.

In addition to the metallocene complex (procatalyst), the metallocene catalyst further comprises a co-catalyst as defined in WO 2015/011135 A1. Accordingly, the preferred cocatalyst is methylalumoxane (MAO) and/or borate, preferably trityl tetrakis(pentafluorophenyl)borate.

It is particularly preferred if the metallocene catalyst is unsupported, ie without the use of an external support. With regard to the preparation of such a metallocene complex, reference is again made to WO 2015/011135 A1.

Product

The invention also relates to a product comprising at least 90.0 wt. % polypropylene composition (P) as defined above.

Preferably, the product includes at least 95.0 wt. % polypropylene composition (P), more preferably at least 97.0 wt. %, even more preferably at least 98.0 wt. %, for example, at least 99.9 wt. %. It is particularly preferred when the article consists of a polypropylene composition (P).

Preferably the article is a film, more preferably a blown film. The film according to the invention can be produced in a conventional manner, for example by cast film technology or blown film technology. More preferably, said product is a single layer or multilayer cast film. Said film usually has a thickness in the range of 15 to 300 µm, preferably in the range of 20 to 250 µm, more preferably in the range of 25 to 200 µm.

Preferably, the film has a pre-steam haze, as measured in accordance with ASTM D 1003-00, measured on a cast film 50 µm thick, below 8.0%, more preferably below 6.0%, even more preferably below 5.0%, for example, below 4.5%, and haze after sterilization, determined in accordance with ASTM D 1003-00, measured on a blown film with a thickness of 50 μm, below 8.0%, more preferably below 6.0%, even more preferably below 4.5%, for example, below 4.0%.

In addition, preferably, the film has a tensile modulus, determined in accordance with ISO 527-3 on a cast film with a thickness of 50 μm, in machine (longitudinal) direction (MD) and/or in transverse direction (TD) of at least 300 MPa , more preferably in the range from 300 to 1000 MPa, even more preferably in the range from 350 to 900 MPa, for example in the range from 400 to 800 MPa.

In addition, preferably, the film has a high relative total energy of penetration per millimeter of thickness that the film can absorb before it breaks divided by the film thickness ( _Wtot ) determined by the Dynatest method according to ISO 7725-2 at 23°C on cast films. 50 µm thick. Said penetration energy ( _Wtot ) may be at least 15.0 J/mm, preferably at least 20.0 J/mm.

It is also preferred that the film has a hot tack strength (SHT) greater than 2.0 N, more preferably greater than 2.5 N.

Application

The invention also relates to the use of an article, preferably a film according to the invention, comprising a polypropylene composition (P) as a sealing layer in a multilayer film.

Such multilayer films are usually obtained by co-extrusion (co-extrusion) cast film. The extrusion coating process can be carried out using conventional co-extrusion cast film techniques. Thus, the polypropylene composition (P) obtained from the polymerization process described above is fed, usually in the form of granules further containing additives, to the extrusion apparatus. From the extruder, the polymer melt is preferably fed through a multilayer flat die to a chill roll for solidification. Co-extrusion is typically performed at a melt temperature of the polypropylene composition (P) in the range of 180 to 260°C and a chill roll temperature in the range of 10 to 60°C. While the polypropylene composition (P) forms one of the outermost layers of said multilayer film, the other layers may include other types of polypropylene and/or polyethylene homo- and/or copolymers.

Other aspects and embodiments of the invention are defined in the following paragraphs: [1] Polypropylene composition (P), comprising at least 90.0 wt. %, based on the total weight of the polypropylene composition (P), copolymer (C) of propylene and 1-hexene, having

i) the total content of 1-hexene in the range from 2.0 to 10.0 wt. %,

ii) melt flow index MFR ₂ determined in accordance with ISO 1133 (2.16 kg, 230°C), in the range from 4.0 to 20.0 g/10 min, and

iii) the amount of 2,1-erythro-regiodefects is at least 0.2 mol%.

[2] The polypropylene composition (P) according to paragraph [1], wherein the copolymer (C) has a xylene-soluble substance (XCS) content of at least 8.0 wt. %.

[3] The polypropylene composition (P) according to paragraph [1] or [2], wherein the copolymer (C) comprises

a) the first random propylene copolymer (A) of propylene and 1-hexene, having a comonomer content in the range from 0.1 to 4.0 wt. %, and

b) a second random propylene copolymer (B) of propylene and 1-hexene having a higher comonomer content than the first random propylene copolymer (A).

[4] The polypropylene composition (P) according to any of the preceding paragraphs, wherein the copolymer (C) has a 1-hexene content in the xylene-soluble C6(XCS) fraction in the range of 2.0 to 15.0 wt. %.

[5] Polypropylene composition (P) according to any of the preceding paragraphs, where the copolymer (C) comprises from 30.0 to 70.0 wt. % of the first random propylene copolymer (A) and from 30.0 to 70.0 wt. % of the second random propylene copolymer (B), based on the total weight of the copolymer (C).

[6] The polypropylene composition (P) according to any one of the preceding paragraphs, wherein the copolymer (C) has a melting point Tm below 140°C.

[7] The polypropylene composition (P) according to any one of the preceding paragraphs, wherein the copolymer (C) corresponds to equation (1)

,

,

where

C6(A) is the content of 1-hexene in the first random propylene copolymer (A) based on the total weight of the first random propylene copolymer (A) [in wt. %];

C6(C) is the content of 1-hexene in the copolymer (C) based on the total weight of the copolymer (C) [in wt. %]; and

[A]/[C] is the weight ratio between the first random propylene copolymer (A) and the copolymer (C) [in g/g]. [8] The polypropylene composition (P) according to any of the preceding paragraphs, wherein the copolymer (C) has been visbreaked with a visbreaking ratio (VR) in the range of 1.5 to 15.0, where the visbreaking is determined in accordance with equation (2)

,

,

in which "MFR _con " is the melt flow rate MFR ₂ determined according to ISO 1133 (230° C., 2.16 kg), copolymer (C) after visbreaking, and "MFR _initial " is the melt flow rate MFR ₂ determined in accordance with ISO 1133 (230°C, 2.16 kg), copolymer (C) before visbreaking.

[9] The polypropylene composition (P) according to paragraph [8], wherein the copolymer (C) has a melt flow index MFR ₂ determined in accordance with ISO 1133 (230°C, 2.16 kg), before visbreaking in the range of 0, 4 to less than 4.0 g/10 min.

[10] Polypropylene composition (P) according to paragraph [8] or [9], where

i) the first random propylene copolymer (A) has an MFR of ₂ (230° C., 2.16 kg) determined according to ISO 1133 before visbreaking in the range of 0.3 to 6.0 g/10 min, and/or

ii) the second random propylene copolymer (B) has an MFR of ₂ (230° C., 2.16 kg) determined according to ISO 1133 before visbreaking in the range of 0.1 to 4.0 g/10 min.

[11] A method for producing a copolymer (C) of propylene and 1-hexene, including the steps

a) obtaining a copolymer (C) of propylene and 1-hexene, having a total content of 1-hexene in the range from 2.0 to 10.0 wt. %, in the presence of a metallocene catalyst (MS),

b) visbreaking the copolymer (C) obtained in step a), with a visbreaking ratio (VR) in the range of 1.5 to 15.0, to obtain a copolymer (C), where the visbreaking is determined in accordance with equation (3)

,

,

in which "MFR(C)" is the melt flow index MFR ₂ determined in accordance with ISO 1133 (230°C, 2.16 kg), copolymer (C) after visbreaking, and "MFR(C')" is melt flow index MFR ₂ determined in accordance with ISO 1133 (230°C, 2.16 kg), copolymer (C).

[12] The method according to paragraph [11], in which the copolymer (C) of propylene and 1-hexene is obtained by

al) polymerizing propylene and 1-hexene in the first reactor (R-1) in the presence of a metallocene catalyst (MC), thereby obtaining a first random propylene copolymer (A) having a content of 1-hexene in the range from 0.1 to 4, 0 wt. %,

a2) transferring said first random propylene copolymer (A) and unreacted comonomers from the first reactor (R-1) to the second reactor (R-2), and

a3) polymerizing propylene and 1-hexene in said second reactor (R-2) and in the presence of said first random propylene copolymer (A) to obtain a second random propylene copolymer (B) having a higher content of 1-hexene than the first random propylene copolymer copolymer (A), wherein said first random propylene copolymer (A) and said second random propylene copolymer (B) form a copolymer (C).

[13] The method according to any one of paragraphs [11] or [12], wherein

i) the melt flow index MFR ₂ determined in accordance with ISO 1133 (230°C, 2.16 kg), copolymer (C) is in the range from 4.0 to 20.0 g/10 min and

ii) the melt flow index MFR ₂ determined in accordance with ISO 1133 (230°C, 2.16 kg), copolymer (C) is in the range from 0.4 to less than 4.0 g/10 min.

[14] The method according to any one of paragraphs [11] to [13], wherein the metallocene catalyst (MC) has the formula (I)

,

,

where

each Cp is independently an unsubstituted or substituted and/or fused cyclopentadienyl ligand, a substituted or unsubstituted indenyl, or a substituted or unsubstituted fluorenyl ligand; wherein the possible one or more substituent(s) are independently selected preferably from halogen, hydrocarbyl (e.g. C1-C20 alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C3-C12 cycloalkyl, C6-C20 aryl or -C20-arylalkyl), C3-C12-cycloalkyl, which contains 1, 2, 3 or 4 heteroatoms (heteroatoms) in the ring group, C6-C20-heteroaryl, C1-C20-haloalkyl, -SiR'' ₃ , -OSiR'' ₃ , -SR'', -PR'' ₂ , -OR'' or -NR'' ₂ ,

each R" is independently hydrogen or hydrocarbyl selected from C1-C20 alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C3-C12 cycloalkyl, or C6-C20 aryl; or in the case of -NR''2 , two substituents R'' may form a five- or six-membered ring together with the nitrogen atom to which they are attached;

R is a bridge of 1-2 C atoms and 0-2 heteroatoms, in which the heteroatom(s) may be Si, Ge and/or O atom(s), where each of the bridge atoms may independently have substituents selected from substituents selected from C1-C20 alkyl, tri(C1-C20 alkyl)silyl, tri(C1-C20 alkyl)siloxy, or C6-C20 aryl; or a bridge of one or two heteroatoms selected from atom(s) of silicon, germanium and/or oxygen,

M is a Group 4 transition metal selected from Zr or Hf, especially Zr;

each X is independently a sigma ligand selected from H, halogen, C1-C20 alkyl, C1-C20 alkoxy, C2-C20 alkenyl, C2-C20 alkynyl, C3-C12 cycloalkyl, C6-C20 aryl , C6-C20-aryloxy, C7-C20-arylalkyl, C7-C20-arylalkenyl, -SR'', -PR'' ₃ , -SiR'' ₃ , -OSiR'' ₃ , -NR'' ₂ or -CH ₂ -Y, where Y is C6-C20-aryl, C6-C20-heteroaryl, C1-C20-alkoxy, C6-C20-aryloxy, -NR'' ₂ , -SR'', -PR'' ₃ , - SiR'' ₃ or -OSiR''₃;

each of the above ring moieties, alone or as part of another moiety as a substituent on Cp, X, R'' or R, may be further substituted with C1-C20 alkyl which may contain Si and/or O atoms; and

n is 1 or 2.

[15] The method according to paragraph [14], wherein the metallocene catalyst (MC) of formula (1) is an organozirconium compound of formula (II) or (II')

,

,

where

M is Zr;

each X is a sigma ligand, preferably each X is independently a hydrogen atom, a halogen atom, a C1-C6 alkoxy group, a C1-C6 alkyl, phenyl or benzyl group;

L is a divalent bridge selected from -R' ₂ C-, -R' ₂ C-CR'2, -R' ₂ Si-, -R' ₂ Si-SiR' ₂ -, -R' ₂ Ge-, where each R' independently represents a hydrogen atom, C1-C20 alkyl, C3-C10 cycloalkyl, tri(C1-C20-alkyl)silyl, C6-C20-aryl or C7-C20 arylalkyl;

each R ² or R ² ' represents a C1-C10 alkyl group;

R ⁵ ' is a C1-C10 alkyl group or a Z'R ³ 'group;

R ⁶ is hydrogen or a C1-C10 alkyl group;

R ⁶ ' represents a C1-C10 alkyl group or a C6-C10 aryl group;

R ⁷ is hydrogen, a C1-C6 alkyl group or a ZR ³ group;

R ⁷ ' represents hydrogen or a C1-C10 alkyl group;

Z and Z' are independently O or S;

R ³ ' represents a C1-C10 alkyl group, or a C6-C10 aryl group, optionally substituted with one or more halogen groups; R ³ is a C1-C10 alkyl group; each n is independently 0 to 4;

and each R ¹ is independently a C1-C20 hydrocarbyl group.

[16] Polypropylene composition (P), comprising at least 90.0 wt. % copolymer (C) obtained by the method according to any of paragraphs [11] - [15].

[17] The product, preferably a film, comprising at least 90.0 wt. % polypropylene composition (P) according to any of paragraphs [1] - [10] or [16].

[18] Use of the article according to paragraph [17] as a sealing layer in a multilayer film.

The invention is further described by way of examples. BUT.

Measurement methods

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

Content ^{of 1} -hexene comonomer in propylene- ¹ -hexene copolymer. ¹³ C, respectively. All spectra were recorded with a ¹³ ° C. optimized 7 mm magic angle rotating probe (MAS) at 180° C. using nitrogen gas for the entire pneumatic system. Approximately 200 mg of material was placed in a 7 mm outer diameter zirconia MAS rotor and rotated at 4 kHz. This setup was chosen primarily because of the high sensitivity required for rapid identification and accurate quantification (Klimke, K., Parkinson, M., Piel, C, Kaminsky, W., Spiess, HW, Wilhelm, M., Macromol. Chem. Phys. 2006;207:382., Parkinson, M., Klimke, K., Spiess, HW, Wilhelm, M., Macromol. Chem. Phys. 2007;208:2128., Castignolles, P., Graf, R., Parkinson, M., Wilhelm, M., Gaborieau, M., Polymer 50 (2009) 2373). Standard single pulse excitation was applied using NOE with short recirculation delays of 3 s (Klimke, K., Parkinson, M., Piel, C, Kaminsky, W., Spiess, HW, Wilhelm, M., Macromol. Chem. Phys. 2006; 207:382., Pollard, M., Klimke, K., Graf, R., Spiess, HW, Wilhelm, M., Sperber, O., Piel, C, Kaminsky, W., Macromolecules 2004;37:813) and RS-HEPT decoupling schemes (Filip, X., Tripon, C, Filip, C, J. Mag. Resn. 2005, 176, 239., Griffin, JM, Tripon, C, Samoson, A., Filip, C, and Brown, SP, Mag. Res. in Chem. 2007 45, SI, S198). In total, 16384 (16k) transitions were obtained in the spectrum.

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

Observed characteristic signals corresponding to the introduction of 1-hexene, and the content of the comonomer was quantified as follows.

The amount of 1-hexene included in isolated PHP sequences was quantified using the integral of αB4 sites at 44.2 ppm, taking into account the number of registration sites per comonomer:

H=IαB4 / 2

The amount of 1-hexene included in the double successive RHHP sequences was quantified using the integral of the ααB4 region at 41.7 ppm, taking into account the number of detection sites per comonomer:

HH=2 * IααВ4

When double sequencing has been observed, it is necessary to compensate for the amount of 1-hexene included in the isolated PHP sequences due to the overlap of the αB4 and αB4B4 signals at 44.4 ppm:

Н=(IαВ4 - 2 * IααВ4) / 2

The total content of 1-hexene is calculated based on the sum of isolated and sequentially included 1-hexene:

Нtotal=Н+НН

When no patches are observed indicating sequential inclusion, then the total content of 1-hexene comonomer is calculated solely for this amount:

Ntot=N

Observed characteristic signals indicating regio-2,1-erythrodefects (Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253).

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

Total secondary (2,1-erythro) propylene incorporated quantified based on the αα21e9 region of methylene at 42.4 ppm: P21=Iαα21e9

The total amount of primary (1.2) incorporated propylene was quantified based on the main Sαα sites of methylene at 46.7 ppm. and with compensation for the relative amount of unaccounted for 2,1-erythro, αB4 and ααB4B4 methylene groups of propylene (note that H and HH are the number of hexene monomers per sequence, and not the number of sequences):

Р12=I _S αα+2*Р21+Н+НН / 2

Total propylene is quantified as the sum of primary (1,2) and secondary (2,1-erythro) propylene incorporated:

Ptot=P12+P21=I _S αα+3* Iαα21e9+(IαB4 - 2 * IααB4) / 2+IααB4

This simplifies to:

Рtot=I _S αα+3* Iαα21e9+0.5*IαB4

The total mole fraction of 1-hexene in the polymer is then calculated as: fH=Htot/(Htot+Ptot)

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

fH=(((IαB4 - 2 * IααB4)/2)+(2 * IααB4))/((I _S αα+3 * Iαα21e9+0.5 * IαB4)+((IαB4 - 2 * IααB4) / 2)+( 2 *IααB4)) It simplifies to:

fH=(IαB4/2+IααB4) / (I _S αα+3* Iαα21е9+IαВ4+IααВ4)

The total mole percent incorporation of 1-hexene comonomer is calculated from the mole fraction in the usual way:

N [mol.%] - 100 * fH

Total 1-hexene comonomer incorporation in mass percent calculated from

mole fraction in the standard way:

H (wt%)=100 * (fH * 84.16) / (fH * 84.16)+(1 - fH) * 42.08))

Calculation of the comonomer content in the second random propylene

copolymer (B):

,

,

where

w(A) - mass fraction of the first random propylene copolymer (A),

w(B) - mass fraction of the second random propylene copolymer (B),

C(A) is the comonomer content (wt %), measured by ¹³ C NMR spectroscopy, in the first random propylene copolymer (A), i.e. in the product of the first reactor (R1),

C(CPP) - comonomer content (wt %), measured by ¹³ C NMR spectroscopy, in the product obtained in the second reactor (R2), i.e. in the mixture of the first random propylene copolymer (A) and the second random propylene copolymer (B) [in propylene copolymer (C-PP)],

C(B) is the calculated comonomer content (wt %) in the second random propylene copolymer (B).

Melt Flow Index (MFR)

Melt flow rates are measured with a load of 2.16 kg (MFR ₂ ) at 230°C. The melt flow index is the amount of polymer in grams that is extruded from an ISO 1133 testing machine for 10 minutes at 230° C. and under a load of 2.16 kg.

Calculation of the melt flow index MFR ₂ (230°C, 2.16 kg) of the second random propylene copolymer (B):

,

,

where

w(A) - mass fraction of the first random propylene copolymer (A),

w(B) - mass fraction of the second random propylene copolymer (B),

MFR (A) - melt flow index MFR ₂ (230°C, 2.16 kg) [in g/10 min], measured in accordance with ISO 1133, the first random propylene copolymer (A),

MFR (C) - melt flow index MFR ₂ (230°C, 2.16 kg) [in g/10 min], measured in accordance with ISO 1133, polypropylene composition (P),

MFR(B) - calculated melt flow rate MFR ₂ (230° C., 2.16 kg) [in g/10 min] of the second random propylene copolymer (B).

Cold xylene solubles (XCS, wt %): Cold xylene solubles (XCS) are determined at 25°C according to ISO 16152; first edition; 2005-07-01.

Hot Hexane Solubles (HHS, wt %) FDA Section 177.1520 1 g of 50 or 100 µm thick polymer film is added to 400 ml of hexane at 50° C. for 2 hours with stirring, under reflux.

After 2 hours, the mixture is immediately filtered through No. 41 filter paper.

The precipitate is collected in an aluminum receiver and the residual hexane is evaporated on a steam bath under N ₂ flow.

The amount of substances soluble in hexane is determined by the formula

((sample mass + crucible mass)-(crucible mass)) / (sample mass) ⋅ 100.

Melting point Tm, crystallization temperature Tcr: measured by differential scanning calorimetry (DSC), Mettler TA820, on samples of 5-10 mg. Curves of crystallization and melting were obtained during the scanning of cooling and heating at a rate of 10°C/min between 30 and 225°C. Peaks of endotherms and exotherms were taken as melting and crystallization temperatures.

Haze was determined according to ASTM D1003-00 on 50 or 100 µm thick cast films produced on a single layer cast film production line with a melt temperature of 220°C and a chill roll temperature of 20°C.

Steam sterilization was carried out in a Systec D series machine (Systec Inc., USA). The samples were heated at a heating rate of 5°C/min starting at 23°C. After 30 minutes at 121° C., they were immediately removed from the steam sterilizer and stored at room temperature until further processing.

Sealing start temperature (TNG); sealing end temperature (TKG); sealing range:

The method determines the sealing temperature range (sealing range) of polypropylene films, in particular blown films or cast films. The sealing temperature range is a temperature range in which films can be sealed according to the conditions below.

The lower limit (Heat Seal Start Temperature (HST)) is the seal temperature at which a seal strength of >5 N is achieved. The upper limit (Seal End Temperature (TST)) is reached when the films adhere to the sealing device.

The seal range is determined using the J&B Universal Sealing Machine Type 3000 on 50 or 100 µm film with the following additional parameters:

Sample Width: 25.4mm Sealing pressure: 0.1 N/ ^mm2 Sealing time: 0.1 s Cooling time: 99 s Peeling speed: 10 mm/s Initial temperature: 80°C Final temperature: 150°С Increments: 10°C

The samples were sealed "A to A" at each temperature of the sealing strip, and determined the strength (strength) of the seal at each stage.

The temperature at which the sealing strength reaches 5 N was determined.

Hot tack strength (SLGS):

Hot tack strength was determined using a J&B Hot Tack Tester on 50 or 100 µm film, with the following additional parameters:

Sample Width: 25.4mm Sealing pressure: 0.3 N/ ^mm2 Sealing time: 0.5 s Cooling time: 99 s Peeling speed: 200 mm/s Initial temperature: 90°С Final temperature: 140°С Increments: 10°С

The maximum stickiness force in the hot state was determined and recorded, that is, the maximum on the force-temperature diagram.

The MD and CD tensile modulus was determined according to ISO 527-3 on cast films 50 or 100 µm thick, with a cross head speed of 1 mm/min.

The impact strength of the cast film was determined by the method "dynamic test (Dynatest)" in accordance with ISO 7725-2 on the film. The "Wbreak" value (J/mm) is the total penetration energy per mm thickness that the film can absorb before it breaks.

2. Examples

Obtaining a catalyst

The catalyst used in example IE according to the invention is prepared as detailed in WO 2015/011135 A1 (metallocene complex MC1 with methylalumoxane (MAO) and borate forming Catalyst 3 described in WO 2015/011135 A1), provided that the surface the active substance is 2,3,3,3-tetrafluoro-2-(1,1,2,2,3,3,3-heptafluoropropoxy)-1-propanol. The metallocene complex (MC1 in WO 2015/011135 A1) is prepared as described in WO 2013/007650 A1 (metallocene E2 in WO 2013/007650 A1).

The catalyst used in comparative example CE2, which is identical to example IE3 according to the invention in EP 2386603 A1, is described in example 1 of EP 1741725 A1.

Obtaining a polypropylene composition (P)

The polypropylene composition (P) was obtained in a sequential manner, including a loop reactor and a gas phase reactor. The reaction conditions are shown in Table 1. Table 2 lists the properties of Comparative Examples and Examples according to the invention.

The polypropylene composition (P) was visbroken in a twin screw extruder using an appropriate amount of t-butylperoxy)-2,5-dimethylhexane (Trigonox 101, from Akzo Nobel, The Netherlands) to achieve the target MFR ₂ as shown in Table 2.

CE1 is a commercial propylene copolymer and 4.5 wt. % ethylene RD208CF from Borealis, having a melt flow rate of 8.0 g/10 min, which is obtained by visbreaking reactor grade PP based on a Ziegler-Natta type catalyst to achieve the target MFR.

As can be seen from Table 2, the haze value after sterilization in the compositions according to the invention, having a content of 1,2-erythro-regio defects above 0.2 mol.%, is significantly lower than the haze value in the comparative example, while the tensile modulus remains at that same level.

Claims (64)

1. Polypropylene composition (P) for a sealing layer in a multilayer film, comprising at least 90.0 wt.%, based on the total weight of the polypropylene composition (P), a copolymer (C) of propylene and 1-hexene having i) the total content of 1-hexene in the range from 2.0 to 10.0 wt.%, ii) melt flow index MFR ₂ determined in accordance with ISO 1133 (2.16 kg, 230°C), in the range from 4.0 to 20.0 g/10 min and iii) the amount of 2,1-erythro-regiodefects is at least 0.2 mol%, wherein the copolymer (C) was visbreaked with a visbreaking ratio (VR) ranging from 1.5 to 15.0, where the visbreaking is determined in accordance with equation (2) VR = PTR _con / PTR _start (2), in which "MFR _con " is the melt flow rate MFR ₂ determined according to ISO 1133 (230°C, 2.16 kg), copolymer (C) after visbreaking and "MFR _initial " is the melt flow rate MFR ₂ , determined according to ISO 1133 (230°C, 2.16 kg), copolymer (C) before visbreaking. 2. The polypropylene composition (P) according to claim 1, wherein the copolymer (C) has a xylene solubles (XCS) content of at least 8.0% by weight. 3. Polypropylene composition (P) according to claim 1 or 2, where the copolymer (C) comprises a) a first random propylene copolymer (A) of propylene and 1-hexene having a comonomer content in the range of 0.1 to 4.0% by weight, and b) a second random propylene copolymer (B) of propylene and 1-hexene having a higher comonomer content than the first random propylene copolymer (A). 4. The polypropylene composition (P) according to any one of the preceding claims, wherein the copolymer (C) has a 1-hexene content in the xylene-solubles C6(XCS) fraction in the range of 2.0 to 15.0 wt%. 5. The polypropylene composition (P) according to any one of the preceding claims, wherein the copolymer (C) comprises from 30.0 to 70.0 wt.% of the first random propylene copolymer (A) and from 30.0 to 70.0 wt.% of the second random propylene copolymer (B) based on the total weight of the copolymer (C). 6. The polypropylene composition (P) according to any one of the preceding claims, wherein the copolymer (C) has a melting point Tm below 140°C. 7. Polypropylene composition (P) according to any one of the preceding claims, wherein the copolymer (C) corresponds to equation (1)

where C6(A) represents the content of 1-hexene in the first random propylene copolymer (A) based on the total weight of the first random propylene copolymer (A) [wt.%]; C6(C) is the content of 1-hexene in the copolymer (C) based on the total weight of the copolymer (C) [wt.%] and [A]/[C] is the weight ratio between the first random propylene copolymer (A) and the copolymer (C) [g/g]. 8. The polypropylene composition (P) according to any one of the preceding claims, wherein the copolymer (C) has a melt flow index MFR ₂ determined in accordance with ISO 1133 (230° C., 2.16 kg) before visbreaking in the range of 0.4 to less than 4.0 g/10 min. 9. Polypropylene composition (P) according to any one of the preceding claims, where i) the first random propylene copolymer (A) has an MFR of ₂ (230° C., 2.16 kg) determined according to ISO 1133 before visbreaking in the range of 0.3 to 6.0 g/10 min and /or ii) the second random propylene copolymer (B) has an MFR of ₂ (230° C., 2.16 kg) determined according to ISO 1133 before visbreaking in the range of 0.1 to 4.0 g/10 min. 10. A method for producing a copolymer (C) of propylene and 1-hexene, including the steps a) obtaining a copolymer (C') of propylene and 1-hexene, having a total content of 1-hexene in the range from 2.0 to 10.0 wt.%, in the presence of a metallocene catalyst (MC), b) visbreaking the copolymer (C') obtained in step a) with a visbreaking ratio (VR) in the range of 1.5 to 15.0 to obtain a copolymer (C), where the visbreaking is determined in accordance with equation (3) VR = MFR(C)/MFR(C') (3), in which "MFR(C)" is the melt flow rate MFR ₂ determined in accordance with ISO 1133 (230°C, 2.16 kg), copolymer (C) after visbreaking and "MFR(C')" is the indicator melt flow MFR ₂ determined in accordance with ISO 1133 (230°C, 2.16 kg), copolymer (C'). 11. The method according to p. 10, in which the copolymer (C') of propylene and 1-hexene is obtained by a1) polymerizing propylene and 1-hexene in the first reactor (R-1) in the presence of a metallocene catalyst (MC), thereby obtaining a first random propylene copolymer (A) having a 1-hexene content in the range from 0.1 to 4.0 wt%, a2) transferring said first random propylene copolymer (A) and unreacted comonomers from the first reactor (R-1) to the second reactor (R-2), and a3) polymerizing propylene and 1-hexene in said second reactor (R-2) and in the presence of said first propylene random copolymer (A) to produce a second propylene random copolymer (B) having a higher 1-hexene content than the first propylene random copolymer copolymer (A), wherein said the first random propylene copolymer (A) and said second random propylene copolymer (B) form a copolymer (C'). 12. The method according to any one of paragraphs. 10 or 11 in which i) the melt flow index MFR ₂ determined in accordance with ISO 1133 (230°C, 2.16 kg), copolymer (C) is in the range from 4.0 to 20.0 g/10 min and ii) the melt flow index MFR ₂ determined in accordance with ISO 1133 (230°C, 2.16 kg), copolymer (C') is in the range from 0.4 to less than 4.0 g/10 min. 13. The method according to any one of paragraphs. 10-12, in which the metallocene catalyst (MC) has the formula (I) R _n (Cp) ₂ MX ₂ (I), where each Cp is independently an unsubstituted or substituted and/or fused cyclopentadienyl ligand, a substituted or unsubstituted indenyl, or a substituted or unsubstituted fluorenyl ligand; wherein the possible one or more substituent(s) are independently selected preferably from halo, hydrocarbyl (e.g. C1-C20 alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C3-C12 cycloalkyl, C6-C20 aryl or C -C20-arylalkyl), C3-C12-cycloalkyl, which contains 1, 2, 3 or 4 heteroatoms (heteroatoms) in the ring group, C6-C20-heteroaryl, C1-C20-haloalkyl, -SiR " ₃ , -OSiR" ₃ , -SR", -PR" ₂ , -OR" or -NR" ₂ , each R" is independently hydrogen or a hydrocarbyl selected from Cl-C20 alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C3-C12 cycloalkyl, or C6-C20 aryl; or in the case of -NR" ₂ , two substituents R" may form a five- or six-membered ring together with the nitrogen atom to which they are attached; R is a bridge of 1-2 C atoms and 0-2 heteroatoms, wherein the heteroatom(s) may be Si, Ge and/or O atom(s), where each of the bridge atoms may independently have substituents selected from substituents selected from Cl-C20 alkyl, tri(C1-C20 alkyl)silyl, tri(C1-C20 alkyl)siloxy, or C6-C20 aryl; or a bridge of one or two heteroatoms selected from atom(s) of silicon, germanium and/or oxygen, M is a Group 4 transition metal selected from Zr or Hf, especially Zr; each X is independently a sigma ligand selected from H, halogen, C1-C20 alkyl, C1-C20 alkoxy, C2-C20 alkenyl, C2-C20 alkynyl, C3-C12 cycloalkyl, C6-C20 aryl , C6-C20-aryloxy, C7-C20-arylalkyl, C7-C20-arylalkenyl, -SR", -PR" ₃ , -SiR" ₃ , -OSiR" ₃ , -NR" ₂ or -CH ₂ -Y, where Y is C6-C20-aryl, C6-C20-heteroaryl, C1-C20-alkoxy, C6-C20-aryloxy, -NR" ₂ , -SR", -PR" ₃ , -SiR" ₃ or -OSiR"₃; each of the above ring moieties, alone or as part of another moiety as a substituent on Cp, X, R" or R, may be further substituted with C1-C20 alkyl which may contain Si and/or O atoms and n is 1 or 2. 14. The method according to p. 13, in which the metallocene catalyst (MC) is an organozirconium compound of formula (II) or (II')

, where M is Zr; each X is a sigma ligand, preferably each X is independently a hydrogen atom, a halogen atom, a C1-C6 alkoxy group, a C1-C6 alkyl, phenyl or benzyl group; L is a divalent bridge selected from -R' ₂ C-, -R' ₂ C-CR' ₂ -, -R' ₂ Si-, -R' ₂ Si-SiR' ₂ -, -R' ₂ Ge- where each R' independently represents a hydrogen atom, C1-C20 alkyl, C3-C10 cycloalkyl, tri(C1-C20-alkyl)silyl, C6-C20-aryl or C7-C20 arylalkyl; each R ² or R ² ' represents a C1-C10 alkyl group; R ⁵ ' is a C1-C10 alkyl group or a Z'R ³ 'group; R ⁶ is hydrogen or a C1-C10 alkyl group; R ⁶ ' represents a C1-C10 alkyl group or a C6-C10 aryl group; R ⁷ is hydrogen, a C1-C6 alkyl group, or a ZR ₃ group; R ⁷ ' represents hydrogen or a C1-C10 alkyl group; Z and Z' are independently O or S; R ³ ' is a C1-C10 alkyl group or a C6-C10 aryl group optionally substituted with one or more halogen groups; R ³ is a C1-C10 alkyl group; each n is independently 0 to 4 and each R ¹ is independently a C1-C20 hydrocarbyl group. 15. Polypropylene composition (P) for a sealing layer in a multilayer film, comprising at least 90.0 wt.% copolymer (C), obtained by the method according to any one of paragraphs. 10-14. 16. Film suitable as a sealing layer in a multilayer film, where the film includes at least 90.0 wt.% polypropylene composition (P) according to any one of paragraphs. 1-9 or 15. 17. Application of the film according to paragraph 16 as a sealing layer in a multilayer film.