RU2792125C1 - Polypropylene film with improved slip properties - Google Patents

Abstract

FIELD: polypropylene film.

SUBSTANCE: invention relates to a method for producing a film containing a polypropylene composition showing improved coefficient of friction and optical properties. A method for producing a film is described, which includes the following steps: i) a propylene homopolymer (HPP) having a melting point (Tm) measured by differential scanning calorimetry (DSC) according to ISO 11357, in the range from 152 to 162°C, cold xylene soluble fraction (XCS) determined at 25°C according to ISO 16152, equal to or less than 1.5 wt.%, and the content of 2,1-erythro-regiodefects, determined using ¹³C-NMR spectroscopy, in the range from 0.01 to 1.00 mol.% polymerized in a multi-stage process in which a loop reactor is followed by a gas phase reactor, in the presence of a metallocene catalyst system comprising: (i') a metallocene catalyst complex of formula (I)

where Mt is Hf or Zr; each X is a sigma ligand, each R¹, identical or different, independently represents a CH₂-R⁷ group, where R⁷ represents H or a linear or branched C_1-6 alkyl group, C_{3- 8} cycloalkyl group, C_6-10 aryl group, each R² independently represents a -CH=, -CY=, -CH₂-, -CHY- or -CY₂ - group, where Y represents a C_1-10 hydrocarbyl group and where n is 2-6, each of R³ and R⁴, the same or different from each other, independently represents hydrogen, a linear or branched C₁-C₆ alkyl group, an OY group, or a C_7-20 arylalkyl, C_7-20 alkylaryl group or a C_6-20 aryl group, wherein at least one R³ per phenyl group and at least one R⁴ is not hydrogen, and optionally two adjacent R³ or R⁴ groups may be part of a ring, containing the carbon atoms of the phenyl group to which they are attached, R⁵ is a linear or branched C₁-C₆-alkyl group, C_7-20 arylalkyl group, C_7-20 alkylaryl group or C₆-C₂₀-aryl group, R⁶ represents a C(R⁸)₃ group, and R⁸ represents a linear or branched C₁-C₆ alkyl group, each R independently represents C₁-C₂₀ hydrocarbyl, C₆-C₂₀ aryl, C₇-C₂₀ arylalkyl, or C₇-C₂₀ alkylaryl, and (ii') a cocatalyst containing a group 13 metal compound, and ii) forming a polypropylene composition into a film containing 95.0-99.9 wt.% of propylene homopolymer (HPP) obtained at stage (i) together with 0.1-0.4 wt.% of a slip additive and 0.0-0.5 wt.% of an anti-block additive.

EFFECT: providing a method for producing films characterized by a low friction coefficient, low turbidity and high transparency.

11 cl, 2 tbl, 4 ex

Description

The invention relates to a film comprising a polypropylene composition having a low dynamic coefficient of friction (Ktr). In addition, the invention relates to a method for producing said film.

Polypropylene is widely used in the field of packaging, including soft packaging. Cast film of polypropylene has the disadvantage of very slow migration of the slip agent compared to, for example, polyethylene. In particular, cast films of visbreaking polypropylenes with a thickness of less than 50 µm do not exhibit sufficiently low CTE after production, which is required for good winding quality as well as for subsequent processing steps. For good winding quality and other production steps, a low CTE is technically necessary and therefore a market requirement.

To meet this requirement in the prior art, it is necessary to add one or more slip additives (in combination with one or more antiblock additives) to polypropylene grades for cast film. The sliding additive migrates to the surface of the film, thus creating a slippery film, which sharply reduces the CTE. Since the migration of slip agent to the surface in polypropylene is very slow, slip agent is added in excess to solve this problem and obtain the required CTE immediately after film production for good winding quality. If less slip agent is added, the CTE immediately after film production is too high and the film must be stored for a long period (about 14 days) to achieve a sufficiently low CTE.

The disadvantages of this solution are:

- high cost due to the excess amount of sliding additive,

- deterioration of the optical properties of the film after a longer period of time due to the fact that too much sliding additive migrates to the surface of the film,

- deposition of sliding additive on the cast film production line in the production of films with a thickness of about 70 μm.

Another well-known approach is the production of polypropylene using a technology using a special catalyst to achieve a lower CTE in the presence of the same amount or even a reduced amount of slip agent.

EP 1747239 describes a process for producing a polypropylene film having a low dynamic coefficient of friction, where a specific catalyst composition is used to polymerize propylene, including a catalyst component in the form of particles having a certain range of sizes.

KR 2001045571 describes a method for producing a film with good sliding properties. This method includes the steps of a) dispersing magnesium ethoxide as a magnesium-based carrier raw material in a mixed solvent of an organic alcohol, a hydrocarbon solvent and an organic phosphorus compound, b) adding anhydrous phthalic acid, c) dropping a titanium tetrachloride solution into a magnesium compound solution and d) collecting the solid component by filtration and adding titanium tetrachloride to the solid component.

US 9701801 also describes a process comprising (1) combining metallocene-catalyzed polypropylene with a nucleator and a lubricant to form a composition, wherein the amount of nucleator in combination with metallocene-catalyzed polypropylene is adjusted to achieve a coefficient of friction (Cfr) less than 0.5; and (2) forming a cast film from the composition wherein the cast film has a coefficient of friction at least 90% less than an otherwise identical cast film lacking a nucleator, the coefficient of friction being measured in accordance with ASTM D1894.

However, in addition to the coefficient of friction (Ktr), good optical properties, in particular low haze and high transparency of the cast film, are usually also required in the field of flexible packaging. It is therefore an object of the invention to provide a cast polypropylene film or a blown polypropylene film having both a low dynamic coefficient of friction and good optical properties, in particular low haze and high transparency.

The above problem is surprisingly solved by providing a film made from a polypropylene homopolymer with a low content of cold xylene soluble fraction (XCS), obtained by polymerization in the presence of a special metallocene catalyst.

Accordingly, the invention provides a film comprising a polypropylene composition containing

a) 95.0-99.9 wt. % propylene homopolymer (HPP) obtained by polymerization in the presence of a metallocene catalyst, while the propylene homopolymer (HPP) has a melting point (Tm) measured using differential scanning calorimetry (DSC), in the range from 152 to 162 ° C, the content of soluble in cold xylene fraction (XCS), determined at 23°C according to ISO 16152, equal to or less than 1.5 wt. %, and has a content of 2,1-erythro-regiodefects, determined using ¹³ C-NMR spectroscopy, in the range from 0.01 to 1.00 mol. %,

b) 0.1-0.4 wt. % of one or more sliding additives, and

c) 0.0-0.5 wt. % of one or more anti-block additives. According to the invention, it has suddenly become possible to use the same

the amount of sliding additive to achieve a reduction in CTE 7 days after production due to the accelerated migration of the sliding additive. In addition, better optical properties of the film are observed, such as a lower haze value.

The film is preferably a non-oriented cast or blown film, more preferably a non-oriented cast film.

In another aspect of the invention, a method for producing a film is provided, comprising the steps of:

i) obtaining a propylene homopolymer (HPP) according to the invention by polymerization in a multi-stage process in which a loop reactor is followed by a gas phase reactor, in the presence of a metallocene catalyst system, and

ii) forming a film of propylene homopolymer (HPP) obtained in step i), together with 0.1-0.4 wt. % of one or more sliding additives and 0.0-0.5 wt. % of one or more anti-blocking agents by using a film casting or blown film process.

Detailed description of the invention

Next, a film including a polypropylene composition, as well as a method for producing the same, will be described in more detail.

Propylene homopolymer (HPP)

According to the invention, the polypropylene composition contains 95.0-99.9 wt. %, preferably 96.0-99.9 wt. %, more preferably from 96.5 to 99.5 wt. % propylene homopolymer (HPP).

The term "propylene homopolymer (HPP)", as used in the invention, refers to polypropylene, which is essentially, that is, more than 98.0 wt. %, preferably more than 99.0 wt. %, even more preferably more than 99.5 wt. %, and even more preferably at least 99.8 wt. %, consists of propylene units. In a preferred embodiment, only propylene units are found in the propylene homopolymer (HPP).

Principally, propylene homopolymer (HPP) is obtained by polymerization in the presence of a metallocene catalyst.

In addition, propylene homopolymer (HPP) is required to have a relatively high melting point Tm. More precisely, it is important that the propylene homopolymer (HPP) has a melting point Tm, measured by differential scanning calorimetry (DSC) according to ISO 11357, in the range from 152 to 162°C. For example, polypropylene homopolymer (HPP) has a melting point Tm, measured by differential scanning calorimetry (DSC) according to ISO 11357, in the range from 152 to 158°C, preferably in the range from 152 to 156°C.

It is also important that the propylene homopolymer (HPP) has a cold xylene soluble fraction (XCS) content equal to or less than 1.5 wt. % based on the total weight of propylene homopolymer (HPP). For example, propylene homopolymer (HPP) has a xylene cold soluble fraction (XCS) content in the range of 0.1 to 1.5 wt. %, preferably in the range from 0.3 to 1.2 wt. %, more preferably in the range from 0.3 to 1.0 wt. %, based on the total weight of propylene homopolymer (HPP).

Preferably, the polypropylene homopolymer (HPP) has an MFR of ₂ (230° C., 2.16 kg), measured according to ISO 1133, in the range of 4.0 to 20.0 g/10 min, preferably in the range 5.0 to 18.0 g/10 min, more preferably in the range of 5.5 to 16.0 g/10 min.

The relatively high melting temperature Tm indicates that propylene homopolymer (HPP) has a fairly low content of regiodefects. Thus, propylene homopolymer (HPP) has a content of 2,1-erythro-regio defects, determined using ¹³ C-NMR spectroscopy, in the range from 0.01 to 1.00 mol. %. More preferably, the propylene homopolymer (HPP) has a content of 2,1-erythro-regio defects, determined using ¹³ C-NMR spectroscopy, in the range from 0.20 to 0.80 mol. % and most preferably in the range from 0.30 to 0.80 mol. %.

Additionally or alternatively, the propylene homopolymer (HPP) has an isotactic triad content (mm) as determined by ¹³ C-NMR spectroscopy of at least 97.5%. For example, propylene homopolymer (HPP) has an isotactic triad content (mm) as determined by ¹³ C-NMR spectroscopy of at least 98.5%, more preferably at least 99.0%, such as, for example, in range from 99.0 to 99.9%.

It is also preferred that the propylene homopolymer (HPP) has a weight average molecular weight (Mw) in the range of 80 to 500 kg/mol, preferably in the range of 100 to 400 kg/mol, more preferably in the range of 120 to 350 k/mol, and/ or a number average molecular weight (Mn) of 20 to 200 kg/mol, more preferably 50 to 150 kg/mol, as determined by gel permeation chromatography (GPC) according to ISO 16014.

Preferably, propylene homopolymer (HPP) has a molecular weight distribution (MWD), measured according to ISO 16014, of ≤ 4.0, preferably in the range of 1.5 to 4.0, more preferably in the range of 2.0 up to 4.0 and most preferably in the range from 2.5 to 4.0. The specified MWD is achieved by polymerization using the specified metallocene catalyst, and not by visbreaking using peroxides or other radical generators.

Preferably, propylene homopolymer (HPP) is obtained by polymerization in the presence of a metallocene catalyst complex of formula (I)

Where

Mt is Hf or Zr;

each X is a sigma ligand,

each R ¹ , identical or different, is independently a CH ₂ -R ⁷ group, wherein R ⁷ is H or a linear or branched C _1-6 alkyl group, a C _3-8 cycloalkyl group, a C _{6 -10} aryl group,

each R ² is independently a -CH=, -CY=, -CH ₂ -, -CHY- or -CY ₂ - group, where Y is a C _1-10 hydrocarbyl group and where n is 2-6,

each of R ³ and R ⁴ , the same or different from each other, is independently hydrogen, a linear or branched C ₁ -C ₆ alkyl group, an OY group or a C _7-20 arylalkyl, a C _7-20 alkylaryl group, or a C _{6- 20} an aryl group, wherein at least one R ³ per phenyl group and at least one R ⁴ is not hydrogen, and optionally two adjacent R or R groups may be part of a ring containing the carbon atoms of the phenyl group to which they are bonded,

R ⁵ is a linear or branched C _1- C ₆ alkyl group, a C _7-20 arylalkyl group, a C _7-20 alkylaryl group, or a C ₆ -C ₂₀ aryl group,

R ⁶ is a C(R ⁸ ) ₃ group, where R ⁸ is a linear or branched C ₁ -C ₆ alkyl group,

each R is independently C ₁ -C ₂₀ hydrocarbyl, C ₆ -C ₂₀ aryl, C ₇ -C ₂₀ arylalkyl, or C ₇ -C ₂₀ alkylaryl.

The catalyst according to the invention can be used in unsupported form or in solid form. The catalyst according to the invention can be used as a homogeneous catalyst or as a heterogeneous catalyst.

The catalyst according to the invention in solid form, preferably in solid particulate form, can either be supported on an external support material such as silica or alumina or, in a particularly preferred embodiment, free of external support but still in solid form. form. For example, a solid catalyst can be obtained by a process in which

(a) forming a liquid/liquid emulsion system, said liquid/liquid emulsion system comprising a solution of components (i) and (ii) of the catalyst dispersed in a solvent so as to form dispersed droplets; and

(b) solidifying said dispersed droplets to form solid particles.

Details of the catalyst used in the invention are described below.

Definitions

Throughout the description, the following definitions are used.

By "free from external carrier" is meant that the catalyst does not contain an external carrier, such as an inorganic carrier such as silica or alumina, or an organic polymeric carrier material.

The term "C _1-20 hydrocarbyl group" includes C _1-20 alkyl, C _2-20 alkenyl, C _2-20 alkynyl, C _3-20 cycloalkyl, C _3-20 cycloalkenyl, C _6-20 aryl groups, C _{7- 20} alkylaryl groups or C _7-20 arylalkyl groups or, of course, mixtures of these groups, such as cycloalkyl substituted with alkyl. Linear and branched hydrocarbyl groups cannot contain cyclic units. Aliphatic hydrocarbyl groups cannot contain aryl rings.

Unless otherwise indicated, preferred C _1-20 hydrocarbyl groups are C _1-20 alkyl, C _4-20 cycloalkyl, C _5-20 cycloalkyl-alkyl groups, C _7-20 alkylaryl groups, C _7-20 arylalkyl groups, or C _{6 -20} aryl groups, especially C _1-10 alkyl groups, C _6-10 aryl groups or C _7-12 arylalkyl groups, for example C _1-8 alkyl groups. The most preferred hydrocarbyl groups are methyl, ethyl, propyl, isopropyl, t-butyl, isobutyl, C _5-6 cycloalkyl, cyclohexylmethyl, phenyl or benzyl.

The term "halo" includes fluoro, chloro, bromo and iodo groups, especially chloro or fluoro groups when it comes to defining a complex.

The oxidation state of a metal ion is determined primarily by the nature of the metal ion in question and the stability of the individual oxidation states of each metal ion.

It should be understood that in the complexes according to the invention, the metal ion M is coordinated with the ligands X in such a way as to match the valency of the metal ion and fill its existing coordination sites. The nature of these σ-ligands can vary greatly.

The terms "C4 phenyl ring" and "C4' phenyl ring" refer to substituted phenyl rings attached to the 4 and 4' positions of the indenyl and indacenyl rings, respectively. The numbering of these rings will be obvious from the structures indicated here.

Catalyst activity is defined herein as the amount of polymer produced/g catalyst/h. Catalyst metal activity is defined here as polymer produced/g metal/h. The term "productivity" is also sometimes used to refer to catalyst activity, although here it refers to the amount of polymer produced per unit mass of catalyst.

The term "molecular weight" is used herein to refer to the weight average molecular weight Mw, unless otherwise indicated.

Detailed description of the catalyst

The metallocene catalyst complexes of the invention are chiral, racemic bridged bis-indenyl C ₁ -symmetrical metallocenes in their anti-configuration. Although the complexes according to the invention are formally C ₁ -symmetric, the complexes ideally retain pseudo-C ₂ symmetry, since they maintain C ₂ symmetry in the immediate vicinity of the metal center, but not at the periphery of the ligand. According to their chemical nature, both anti- and syn-enantiomeric pairs are formed during the synthesis of complexes (in the case of C ₁ -symmetric complexes). For the purposes of the invention, "racemic-anti" means that the two indenyl ligands are oriented in opposite directions relative to the cyclopentadienyl-metal-cyclopentadienyl plane, while "racemic-syn" means that the two indenyl ligands are oriented in the same direction relative to the cyclopentadienyl-metal plane. -cyclopentadienyl, as shown in the diagram below.

Formula (I) and any special cases of the formula provide for the inclusion of both syn- and anti-configurations. Preferred metallocene catalyst complexes are in the anti-configuration.

The metallocene catalyst complexes according to the invention are used as racemic anti-isomers. Ideally, therefore, at least 95 mol.%, for example, at least 98 mol.%, in particular at least 99 mol%. metallocene catalytic complex, is in racemic-anti-isomeric form.

The following preferences apply to the metallocene catalyst complexes of the invention. The metallocene catalyst complexes according to the invention have the formula (I):

In the complex of formula (I), it is preferred if Mt is Zr or Hf, preferably Zr;

Each X is a sigma ligand. Most preferably, each X is independently a hydrogen atom, a halogen atom, a C _1-6 alkoxy group, or an R' group, where R' is a C _1-6 alkyl, phenyl, or benzyl group. Most preferably X is chloro, benzyl or methyl. Preferably, both X groups are the same. The most preferred embodiments are two chlorides, two methyl or two benzyl groups, especially two chlorides.

In the formula -SiR ₂ -, each R is independently C ₁ -C ₂₀ hydrocarbyl, C ₆ -C ₂₀ aryl, C ₇ -C ₂₀ arylalkyl, or C ₇ -C ₂₀ alkylaryl. Thus, the term "C _1-20 hydrocarbyl group" includes C _1-20 alkyl, C _2-20 alkenyl, C _2-20 alkynyl, C _3-20 cycloalkyl, C _3-20 cycloalkenyl, C _6-20 aryl groups, C _7-20 alkylaryl groups or C _7-20 arylalkyl groups or, of course, mixtures of these groups, such as cycloalkyl substituted with alkyl. Unless otherwise indicated, preferred C _1-20 hydrocarbyl groups are C _1-20 alkyl, C _4-20 cycloalkyl, C _5-20 cycloalkyl-alkyl groups, C _7-20 alkylaryl groups, C _7-20 arylalkyl groups, or C _{6 -20} aryl groups.

Preferably, both R groups are the same. Preferably R is a C ₁ -C ₁₀ hydrocarbyl or C ₆ -C ₁₀ aryl group such as methyl, ethyl, propyl, isopropyl, t-butyl, isobutyl, C _5-6 cycloalkyl, cyclohexylmethyl, phenyl or benzyl , more preferably both R are C _{1 -C 6} -alkyl, C ₃ - ₈ cycloalkyl or C ₆ -aryl group, such as C ₁ -C ₄ -alkyl, C _5-6 cycloalkyl or C ₆ -aryl group, and most preferably both R's are methyl or one is methyl and the other is cyclohexyl. Most preferably the bridge is -Si(CH ₃ ) ₂ -.

Each R ¹ , identical or different, is independently a CH ₂ -R ⁷ group, wherein R ⁷ is H or a linear or branched C _1-6 alkyl group such as methyl, ethyl, n-propyl, isopropyl. n-butyl, isobutyl, sec-butyl and tert-butyl or C _3-8 cycloalkyl group (eg cyclohexyl), C _6-10 aryl group (preferably phenyl);

Preferably both R ¹ are the same and are a CH ₂ -R ⁷ group, wherein R ⁷ is H or a linear or branched C ₁ -C ₄ alkyl group, more preferably both R ¹ are the same and are a CH ₂ -R group ⁷ , wherein R ⁷ is H or a straight or branched C _1- C ₃ alkyl group. Most preferably, both R ¹ are methyl.

Each R ² is independently a -CH=, -CY=, -CH ₂ -, -CHY- or -CY ₂ - group, where Y is a C _1-10 hydrocarbyl group, preferably a C _1-4 hydrocarbyl group, and where n is 2-6, preferably 3-4.

Each of the substituents R ³ and R ⁴ , which are the same or different from each other, is independently hydrogen, a linear or branched C _1- C ₆ alkyl group, an OY group, or a C _7-20 arylalkyl, C _7-20 alkylaryl group, or C _{a 6-20} aryl group, preferably hydrogen, a linear or branched C ₁ -C ₆ alkyl group, or a C _6-20 aryl group, and optionally two adjacent R ³ or R ⁴ groups may be part of a ring containing the carbon atoms of the phenyl group, with which they are associated. More preferably, R ³ and R ⁴ are hydrogen or a linear or branched C ₁ -C ₄ alkyl group or an OY group, where Y is a C _1-4 hydrocarbyl group. Even more preferably, each R ³ and R ⁴ independently represents hydrogen, methyl, ethyl, isopropyl, t-butyl or methoxy, in particular hydrogen, methyl or t-butyl, with at least one R ³ per phenyl group and at least one R ⁴ is not hydrogen.

Thus, preferably one or two R ³ per phenyl group is not hydrogen, more preferably the same R ³ on both phenyl groups, such as, for example, 3',5'-di-methyl or 4'-tert-butyl for both phenyl groups. groups.

For the indenyl moiety, preferably one or two R ⁴ on the phenyl group is not hydrogen, more preferably two R ⁴ are not hydrogen, and most preferably the two R ⁴ are the same, for example, 3',5'-di-methyl or 3',5' -di-tert-butyl.

R ⁵ is a linear or branched C _{1 -C 6} alkyl group such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and tert-butyl, C _7-20 arylalkyl, C _{7 -20} alkylaryl group or Ce-C ₂₀ aryl group.

R ⁵ is preferably a linear or branched C _{1 -C 6} alkyl group or a C _6-20 aryl group, more preferably a linear C ₁ -C ₄ alkyl group, even more preferably a C ₁ -C ₂ alkyl group, and most preferably methyl.

R ⁶ is a C(R ⁸ ) ₃ group, where R ⁸ is a linear or branched C _1- C ₆ alkyl group.

Each R is independently C ₁ -C ₂ o-hydrocarbyl, C ₆ -C ₂₀ aryl, C7-C ₂ 0-arylalkyl, or C7-C ₂ o-alkylaryl. Preferably R ⁸ are the same or different, each R ⁸ is a linear or branched C ₁ -C 4 alkyl group, more preferably R ⁸ are the same and represent a C ₁ -C ₂ alkyl group. Most preferably, all R ⁸ groups are methyl.

In a preferred embodiment, the invention provides a metallocene catalyst complex of formula (1a)

where each of R ³ and R ⁴ identical or different from each other, independently represents hydrogen or a linear or branched C ₁ -C ₆ -alkyl group, with at least one R ³ per phenyl group and at least one R ⁴ is not hydrogen.

Specific metallocene catalyst complexes of the invention include:

rac-anti-dimethylsilandiyl[2-methyl-4,8-bis-(4'-tert-butylphenyl)-1,5,6,7-tetrahydro-s-indacen-1-yl][2-methyl-4-(3 ',5'-dimethylphenyl)-5-methoxy-6-tert-butylinden-1-yl] zirconium dichloride

rac-anti-dimethylsilandiyl[2-methyl-4,8-bis-(3',5'-dimethylphenyl)-1,5,6,7-tetrahydro-s-indacen-1-yl][2-methyl-4 -(3',5'-dimethylphenyl)-5-methoxy-6-tert-butylinden-1-yl] zirconium dichloride

rac-anti-dimethylsilandiyl[2-methyl-4,8-bis-(3',5'-dimethylphenyl)-1,5,6,7-tetrahydro-s-indacen-1-yl][2-methyl-4 -(3',5'-ditretbutyl-phenyl)-5-methoxy-6-tert-butylinden-1-yl]zirconium dichloride

or their corresponding analogues, including zirconium dimethyl.

Throughout the foregoing description, where a narrower definition of a substituent is provided, that narrower definition is deemed to be disclosed in conjunction with all broader and narrower definitions of other substituents in the application.

Synthesis

The ligands needed to form the catalysts of the invention can be synthesized by any method, and one skilled in the art of organic chemistry will be able to design various synthetic protocols to prepare the necessary ligand materials. WO 2007/116034 describes the necessary chemistry and is incorporated herein by reference. Synthesis protocols can also be found generally in WO 2002/02576, WO 2011/135004, WO 2012/084961, WO 2012/001052, WO 2011/076780 and WO 2015/158790. The section relating to examples also provides the skilled person with sufficient guidance.

A method for producing a ligand of a metallocene catalytic complex of formula (I or Ia) containing two substituents - (R ³ ) ₃ -phenyl groups.

Synthesis of a ligand of a metallocene catalytic complex of formula (I or Ia) containing two substituents - (R ³ ) ₃ -phenyl groups, preferably the synthesis of an indacenyl ligand.

The metallocene ligand described in PCT/EP 2017/084273 includes two different indenes, one methoxyindene and one indacene. The synthesis of methoxyindene is simple and gives high yield, while the synthesis of indacene requires several steps, as shown in Scheme 1 for the case of 4-(4-tert-butylphenyl)indacene:

Scheme 1

A ligand of a metallocene catalyst complex of formula (I or Ia) containing two (R ³ ) ₃ -phenyl groups as substituents, preferably an indacene ligand used in the synthesis of metallocene catalyst complexes according to the invention, which is a structural analogue of the above structure, is obtained with a number of stages per one less, as shown in diagram 2:

Thus, the new metallocene catalyst complexes according to the invention can be obtained in a simpler way, and also, as shown in the experimental part, in a more efficient way.

Therefore, the present invention also relates to a process for the preparation of a metallocene catalyst complex ligand of formula (I or Ia) containing two (R ³ ) ₃ -phenylene groups as substituents, preferably an indacene ligand.

This method, similar to scheme 2, contains the following steps:

1. Electrophilic dibromination of the starting keto compound, for example R ¹ -3,5,6,7-tetrahydro-s-indecen-1(2H)-one

2. Reduction of the corresponding dibromo compound, for example 4,8-dibromo-R ¹ -3,5,6,7-tetrahydro-s-indecen-1(2H)-one, followed by methylation to give the corresponding OMe compound

3. The combination of Kumada with (R ³ ) ₃ -phenylmagnesium bromide and

4. Demethoxylation

Step 1 is preferably carried out with aluminum chloride in dichloromethane at a low temperature, such as from 2 to 10°C, for example about +5°C.

The reduction in step 2 is preferably carried out with sodium borohydride in THF-MeOH at low temperature, such as from 2 to 10°C, for example about +5°C.

The methylation is preferably performed at room temperature with MeI/KOH/DMSO.

Step 3 is preferably carried out in the presence of a NiCl ₂ (PPh ₃ )IPr catalyst at reflux temperature, and step 4 is preferably carried out with a catalytic amount of TsOH in toluene at reflux temperature.

cocatalyst

In order to form active catalyst species, it is usually necessary to use a co-catalyst, as is well known in the art.

According to the invention, a co-catalyst system comprising a boron-containing co-catalyst and/or an alumoxane co-catalyst is used in combination with a metallocene catalyst complex as defined above.

The aluminoxane cocatalyst may be a cocatalyst of formula (X):

where n is usually from 6 to 20 and R has the meaning given below.

Alumoxanes are formed by the partial hydrolysis of organoaluminum compounds, for example compounds of the formula AlR ₃ , AlR ₂ Y and Al ₂ R ₃ Y ₃ , where R may be, for example, C _{1 -C 10} alkyl, preferably C ₁ -C ₅ alkyl, or C _3-10 cycloalkyl, C ₇ -C ₁₂ arylalkyl or alkylaryl and/or phenyl or naphthyl, and where Y can be hydrogen, halogen, preferably chlorine or bromine, or C ₁ -C ₁₀ alkoxy, preferably methoxy or ethoxy. The resulting oxygenated alumoxanes are generally not pure compounds, but mixtures of oligomers of formula (X).

A preferred alumoxane is methylalumoxane (MAO). Since the alumoxanes used as co-catalysts according to the invention are not pure compounds due to the way they are prepared, the molarity of the alumoxane solutions is hereafter based on their aluminum content.

According to the invention, a boron-containing co-catalyst can also be used instead of an alumoxane co-catalyst, or an alumoxane co-catalyst can be used in combination with a boron-containing co-catalyst.

The person skilled in the art will appreciate that when boron-based co-catalysts are used, it is common to pre-alkylate the complex by reacting it with an aluminum alkyl compound such as triisobutylaluminum (TIBA). This procedure is well known and any suitable aluminum alkyl may be used, eg Al(C _1-6 alkyl) ₃ . Preferred alkyl aluminum compounds are triethylaluminum, triisobutylaluminum, triisohexylaluminum, tri-n-octylaluminum and triisooctylaluminum.

Alternatively, when using a borate co-catalyst, the metallocene catalyst complex is present in alkylate form, ie, for example, a dimethyl or dibenzyl metallocene catalyst complex can be used.

Boron based cocatalysts of interest include cocatalysts of formula (Z)

BY ₃ (Z)

where Y, the same or different, represents a hydrogen atom, an alkyl group of 1 to about 20 carbon atoms, an aryl group of 6 to about 15 carbon atoms, alkylaryl, arylalkyl, haloalkyl, or haloaryl, each containing from 1 to 10 carbon atoms in an alkyl radical and from 6 to 20 carbon atoms in an aryl radical, or fluorine, chlorine, bromine or iodine. Preferred examples for Y are methyl, propyl, isopropyl, isobutyl or trifluoromethyl, unsaturated groups such as aryl or haloaryl, for example phenyl, tolyl, benzyl groups, p-fluorophenyl, 3,5-difluorophenyl, pentachlorophenyl, pentafluorophenyl, 3, 4,5-trifluorophenyl and 3,5-di(trifluoromethyl)phenyl. Preferred options are trifluoroborane, triphenylborane, tris(4-fluorophenyl)borane, tris(3,5-difluorophenyl)borane, tris(4-fluoromethylphenyl)borane, tris(2,4,6-trifluorophenyl)borane, tris(pentafluorophenyl)borane , tris(tolyl)borane, tris(3,5-dimethylphenyl)borane, tris(3,5-difluorophenyl)borane and/or tris(3,4,5-trifluorophenyl)borane.

Particular preference is given to tris(pentafluorophenyl)borane.

However, it is preferable to use borates, ie compounds containing a 3+ borate ion. Such ionic cocatalysts preferably contain a non-coordinating anion such as tetrakis(pentafluorophenyl)borate and tetraphenylborate. Suitable counterions are protonated amine or aniline derivatives such as methylammonium, anilinium, dimethylammonium, diethylammonium, N-methylanilinium, diphenylammonium, N,N-dimethylanilinium, trimethylammonium, triethylammonium, tri-n-butylammonium, methyldiphenylammonium, pyridinium, p-bromo-N ,N-dimethylanilinium or p-nitro-N,N-dimethylanilinium.

Preferred ionic compounds that can be used according to the invention include:

triethylammonium tetra(phenyl)borate, tributylammoniumtetra(phenyl)borate,

trimethylammonium tetra(tolyl) borate, tributylammonium tetra(tolyl) borate,

tributylammonium tetra(pentafluorophenyl)borate,

tripropylmmonitra(dimethylphenyl)borate,

tributyl ammonium tetra(trifluoromethylphenyl)borate,

tributylammonium tetra(4-fluorophenyl)borate,

N,N-dimethylcyclohexylammoniumtetrakis(pentafluorophenyl)borate,

N,N-dimethylbenzylmmmoniumtetrakis(pentafluorophenyl)borate,

N,N-dimethylanilinium tetra(phenyl)borate,

N,N-diethylanilinium tetra(phenyl) borate,

N,N-d imethyl anil initetr akis (pentafluorophenyl) borate,

N,N-di(propyl)ammoniumtetrakis(pentafluorophenyl)borate,

di(cyclohexyl)ammoniumtetrakis(pentafluorophenyl)borate,

triphenylphosphoniumtetrakis(phenyl)borate, triethylphosphoniumtetrakis(phenyl)borate,

diphenylphosphoniumtetrakis(phenyl)borate,

tri(methylphenyl)phosphoniumtetrakis(phenyl)borate,

tri(dimethylphenyl)phosphoniumtetrakis(phenyl)borate,

triphenylcarbeniumtetrakis(pentafluorophenyl)borate,

or ferroceniumtetrakis(pentafluorophenyl)borate.

Preference is given to triphenylcarbeniumtetrakis(pentafluorophenyl)borate,

N,N-dimethylcyclohexylammoniumtetrakis(pentafluorophenyl)borate or

N,N-dimethylbenzylammoniumtetrakis(pentafluorophenyl)borate.

It has surprisingly been found that certain boron co-catalysts are particularly preferred. Thus, the preferred borates used in the invention contain trityl ion. Thus, the use of N,N-dimethylammonium tetrakispentafluorophenyl borate and Ph ₃ CB(PhF ₅ ) ₄ and analogues thereof is therefore particularly preferred.

According to the invention, the preferred cocatalysts are alumoxanes, more preferably methylalumoxanes, combinations of alumoxanes with Al-alkyls, boron or borate cocatalysts, and combinations of alumoxanes with boron-based cocatalysts.

Suitable amounts of cocatalyst are well known to those skilled in the art.

The molar ratio of boron to metallocene metal ion can range from 0.5:1 to 10:1 mol/mol, preferably from 1:1 to 10:1, in particular from 1:1 to 5:1 mol/mol.

The molar ratio of A1 in alumoxane to metallocene metal ion may range from 1:1 to 2000:1 mol/mol, preferably from 10:1 to 1000:1, and more preferably from 50:1 to 500:1 mol/mol.

Catalyst preparation

The metallocene catalyst complex of the invention can be used in combination with a suitable co-catalyst as a propylene polymerization catalyst, for example in a solvent such as toluene or an aliphatic hydrocarbon (i.e. for solution polymerization), as is well known in the art. Preferably the polymerization of propylene takes place in the condensed phase or in the gas phase. The catalyst according to the invention can be used in supported or unsupported form. The particulate carrier material used is preferably an organic or inorganic material such as silica, alumina or zirconium oxide, or a mixed oxide such as aluminosilicate, in particular silica, alumina or aluminosilicate. The use of a silica carrier is preferred. The person skilled in the art is aware of the procedures necessary for applying a metallocene catalyst.

Particularly preferably, the support is a porous material so that the complex can be loaded into the pores of the support, for example using a process similar to those described in WO 94/14856, WO 95/12622 and WO 2006/097497. The particle size is not critical, but is preferably in the range of 5 to 200 µm, more preferably 20 to 80 µm. The use of these carriers is conventional in the art.

In an alternative embodiment, no carrier is used at all. Such a catalyst can be prepared in solution, for example, in an aromatic solvent such as toluene, by contacting the metallocene (as a solid or as a solution) with a co-catalyst, for example, methylalumoxane, or borane or borate salt, previously dissolved in an aromatic solvent, or can be obtained by successively adding dissolved catalyst components to the polymerization medium.

In one embodiment, no external support is used, but the catalyst is still in particulate form. Thus, no external carrier material is used, such as an inert organic or inorganic carrier, such as silica, as described above.

In order to provide the catalyst according to the invention in solid form, but without the use of an external carrier, it is preferred if a liquid/liquid emulsion system is used. The method includes forming dispersible catalyst components (i) and (ii) in a solvent and solidifying said dispersed droplets to form solid particles.

In particular, the method includes preparing a solution of one or more components of the catalyst; dispersing said solution in a solvent to form an emulsion in which said one or more catalyst components are present in droplets of the dispersed phase; immobilizing the catalyst components in dispersed droplets in the absence of an external porous particulate carrier to form solid particles comprising said catalyst, and optionally recovering said particles.

This method allows the production of active catalyst particles with improved morphology, for example, with a desired spherical shape, surface properties and particle size, and without the use of any added external porous carrier material, such as an inorganic oxide, for example, silicon dioxide. By "preparing a solution of one or more catalyst components" is meant that the catalyst-forming compounds may be combined in a single solution which is dispersed in an immiscible solvent, or alternatively at least two separate catalyst solutions may be prepared for each portion of the catalyst-forming compounds. , which are then successively dispersed in the solvent.

A full disclosure of the necessary method can be found in WO 03/051934, which is incorporated herein by reference.

The invention is also commercially advantageous in that it allows the production of solids by a single reactor scheme. Continuous or semi-continuous processes are also possible for the preparation of the catalyst.

Autonomous ("offline") prepolymerization on a catalyst

The use of heterogeneous catalysts where no external support material is used (also referred to as "self-supporting" catalysts) may have the disadvantage of tending to dissolve to some extent in the polymerization medium, i.e. some active catalyst components may leach out of the catalyst particles during slurry polymerization. , whereby the original good morphology of the catalyst may be lost. These leached catalyst components are very active and can cause problems during polymerization. Therefore, the amount of leached components must be kept to a minimum, ie all catalyst components must be kept in a heterogeneous form.

In addition, self-sustaining catalysts, due to the large amount of catalytically active substances in the catalyst system, generate high temperatures at the start of polymerization, which can cause melting of the product material. Both effects, i.e. partial dissolution of the catalyst system and generation of heat, can lead to fouling, fouling and deterioration of the morphology of the polymer material.

To minimize the potential problems associated with high activity or leaching, an "offline (offline) prepolymerization" can be performed on the catalyst prior to its use in the polymerization process.

It should be noted that offline prepolymerization is in this respect part of the catalyst preparation process, being a step carried out after the formation of the solid catalyst. The offline catalyst prepolymerization step is not part of the configuration of the actual polymerization process containing the prepolymerization step. After the stage offline (offline) pre-polymerization on the catalyst, the solid catalyst can be used in the polymerization.

"Offline (offline) pre-polymerization" on the catalyst is performed after the solidification step of the liquid-liquid emulsion process. The prepolymerization can be carried out by known methods described in the prior art, such as the method described in WO 2010/052263, WO 2010/052260 or WO 2010/052264. Preferred embodiments of this aspect of the invention are described herein.

Preferably, alpha-olefins are used as monomers in the offline prepolymerization on a catalyst. Preferably, C ₂ -C ₁₀ olefins are used, such as ethylene, propylene, 1-butylene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, 1-nonene, 1-decene , styrene and vinylcyclohexene. The most preferred alpha-olefins are ethylene and propylene, especially propylene.

The offline catalysed prepolymerization can be carried out in gas phase or in an inert diluent, typically an oil or a fluorinated hydrocarbon, preferably a fluorinated hydrocarbon or mixture of fluorinated hydrocarbons. Preferably, perfluorinated hydrocarbons are used. The melting temperature of such (per)fluorinated hydrocarbons is usually in the range from 0 to 140°C, preferably from 30 to 120°C, for example, from 50 to 110°C.

If the offline prepolymerization on a catalyst is carried out in fluorinated hydrocarbons, the temperature in the prepolymerization stage is below 70°C, for example in the range of -30 to 70°C, preferably 0 to 65°C and more preferably in the range of 20 up to 55°С. The pressure inside the reaction vessel is preferably above atmospheric pressure to minimize the possible entry of air and/or moisture into the catalyst vessel. Preferably the pressure is in the range of at least 1 to 15 bar (at least 0.1 to 1.5 MPa), preferably 2 to 10 bar (0.2 to 1 MPa). The reaction vessel is preferably kept under an inert atmosphere such as nitrogen or argon or the like.

The offline (offline) prepolymerization is continued until the desired degree of prepolymerization, defined as weight of polymer matrix/weight of solid catalyst prior to the prepolymerization step, is reached. This degree is less than 25, preferably 0.5 to 10.0, more preferably 1.0 to 8.0, most preferably 2.0 to 6.0.

The use of an offline catalyst prepolymerization step provides the advantage of minimizing leaching of catalyst components and hence local overheating.

After offline prepolymerization, the catalyst can be isolated and stored.

Polymerization

Propylene homopolymer (HPP) is preferably produced in a single or multi-stage propylene polymerization process such as bulk polymerization, gas phase polymerization, slurry polymerization, solution polymerization, or combinations thereof. Preferably, propylene homopolymer (HPP) can be produced in a combination of a loop and a gas phase reactor. These methods are well known to the person skilled in the art.

The preferred multi-stage process is the "loop-gas-phase" process such as that developed by Borealis (known as the BORSTAR® technology) described for example in patent literature such as EP 0 887 379, WO 92/12182, WO 2004/000899, WO 2004 /111095, WO 99/24478, WO 99/24479 or WO 00/68315.

Another suitable slurry gas phase process is the Spheripol® Basell process.

Preferably, in the fast process for producing the C ₂ C ₃ random copolymer composition described above, the conditions in the first reactor (R-1), that is, a slurry reactor (SR) such as a loop reactor (LR), in step (a) may be the following:

- the temperature is in the range from 40°C to 110°C, preferably between 60°C and 100°C, more preferably between 65 and 95°C,

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

- hydrogen can be added to control the molar mass in a known manner.

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

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

- the pressure is in the range from 5 bar to 50 bar (from 0.5 MPa to 5 MPa), preferably between 15 bar and 35 bar (from 1.5 MPa to 3.5 MPa),

- hydrogen can be added to control the molar mass in a known manner.

Polypropylene composition

The polypropylene composition according to the invention contains 0.1-0.4 wt. %, preferably from 0.1 to 0.35 wt. %, more preferably from 0.1 to 0.3 wt. % of one or more sliding additives and 0.0-0.5 wt. %, preferably from 0.1 to 0.4 wt. %, more preferably from 0.1 to 0.3 wt. % of one or more anti-block additives.

Glidants are also widely known in the art. Glidants migrate to the surface and act as lubricants between polymer and polymer and between polymer and metal rolls, resulting in a reduced coefficient of friction (Cfr). Examples are fatty acid amides such as erucamide (CAS No. 112-84-305), oleamide (CAS No. 301-02-0), stearamide (CAS No. 124-26-5), or combinations thereof. A complete list of suitable slip additives can be found in Chapter 8 "Gliding Additives" of the "Plastic Additives Handbook" edited by H. Zweifel, RD Maier and M. Schiller, ^6th edition, X. Zweifel. , R.D. Mayer and M. Schiller, 6th edition), Hanser Publishers 2009, pp. 629-636.

Common anti-block additives are natural silica such as diatomaceous earth (e.g. CAS No. 60676-86-0 (SuperfFloss™), CAS No. 60676-86-0 (SuperFloss E™) or CAS No. 60676- 86-0 (Celite 499™)), synthetic silica (such as CAS No. 7631-86-9 or CAS No. 112926-00-8), silicates (such as aluminum silicate (Kaolin) CAS No. 1318-74 -7, sodium aluminum silicate CAS No. 1344-00-9, calcined kaolin CAS No. 92704-41-1, aluminum silicate CAS No. 1327-36-2 or calcium silicate CAS No. 1344-95-2), synthetic zeolites (such as sodium calcium aluminum silicate hydrate CAS No. 1344-01-0). A complete list of suitable anti-blocking additives can be found in Chapter 7, Anti-blocking Additives, of the Plastic Additives Handbook, edited by H. Zweifel, RD Maier and M. Schiller, 6 ^th edition, under edited by X. Zweifel, R.D. Mayer and M. Schiller, 6th edition), Hanser Publishers 2009, pp. 613-628.

In a preferred embodiment, the polypropylene composition may further contain one or more additives in a total amount of from 0.1 to 5.0 wt. % based on the composition, while the additive is selected from the group including UV stabilizers, antistatic additives, alpha-nucleating additives and antioxidants.

Such additives are widely known to the person skilled in the art.

Examples of antioxidants commonly used in the art are hindered phenols (such as CAS No. 6683-19-8, also sold as Irganox 1010 FF™ from BASF), phosphorus-based antioxidants (such as CAS No. 31570-04 -4, also sold as Hostanox PAR 24 (FF)™ by Clariant or Irgafos 168 (FF)™ by BASF), sulfur-based antioxidants (such as CAS No. 693-36-7, sold as Irganox PS-802 FL™ from BASF), nitrogen-based antioxidants (such as 4,4'-bis(1,1'-dimethylbenzyl)diphenylamine), or mixtures of antioxidants.

Acid scavengers are also widely known in the art. Examples are calcium stearates, sodium stearates, zinc stearates, magnesium and zinc oxides, synthetic hydrotalcite (e.g. SHT, C AS No. 11097-59-9), lactates and lactylates, and calcium stearate (CAS No. 1592-23- 0) and zinc stearate (CAS No. 557-05-1).

Suitable UV stabilizers are, for example, bis-(2,2,6,6-tetramethyl-4-piperidyl)-sebacate (CAS No. 52829-07-9, Tinuvin 770); 2-hydroxy-4-n-octoxy-benzophenone (CAS No. 1843-05-6, Chimassorb 81).

Alpha-nucleating agents such as sodium benzoate (CAS No. 532-32-1) may also be added; a mixture of aluminum hydroxy-bis[2,2'-methylene-bis(4,6-di-tert-butylphenyl)phosphate] and lithium myristate (commercially available as Adekastab NA-21 from Adeka Palmarole, France) or 1.3:2, 4-bis(3,4-dimethylbenzylidene)sorbitol (CAS No. 135861-56-2, commercially available as Millad 3988 from Milliken, USA).

Suitable antistatic agents are, for example, glycerol esters (CAS No. 97593-29-8) or ethoxylated amines (CAS No. 71786-60-2 or 61791-31-9) or ethoxylated amides (CAS No. 204-393- 1).

Typically, these additives are added in amounts of 100-1000 ppm for each individual component. Preferably, at least an antioxidant is added.

The polypropylene composition of the invention may be compounded and granulated using any of a variety of compounding and mixing machines and methods well known and widely used in the resin compounding art. To mix the individual components of the proposed polypropylene composition, you can use a conventional compounding or mixing device, for example, a Banbury mixer, twin roll rubber mixing rolls, Buss mixer or twin screw extruder. Preferably, a co-rotating twin screw extruder is used. Polypropylene compositions obtained from the extruder/mixer are usually in the form of granules. These granules are then further processed and formed into a film according to the invention.

Film

The polypropylene compositions described above are suitable for the production of blown films as well as cast films.

Description of blown film production

The composition described above can be used to produce blown films with water or air quench, preferably air quenched blown films, on conventional blown film equipment.

In principle, the method includes the steps:

(i) inflating the tube of molten material with air perpendicular to the upward direction from the side-fed film die for blown extrusion;

(ii) cooling it with a water contact cooling ring or air quench;

(iii) folding it up and passing it through the take-off rollers to the winder.

Blown Film Technology with Water Contact Cooling Ring

In this polymer film technology, the molten mixture is extruded through a tubular die fed by a (usually single screw) extruder and blown into a tube. The film tube is in contact with the water cooling ring on the outside and cools quickly. The already hardened film tube is then flattened by take-up rolls and transferred to a winder.

For a more detailed description, see "Polypropylene Handbook", edited by Edward P. Moore, Jr. ("Handbook of Polypropylene", edited by Edward P. Moore, Jr.), Hanser Publishers, 1996.

Air-quench blown film technology

At this stage in the manufacture of air-tempered blown films, the films are made using a blow-up ratio of at least 1.5, preferably a blow-up ratio of at least 2.0, more preferably a blow-up ratio of at least 2.5.

The blown film extrusion technology with air quenching is well known for the production of thin plastic films. In a preferred process, the mixtures described above are extruded through a circular die to form a film. Air is introduced through the center of the die to maintain the film in the form of a bubble, which increases the diameter of the film by about 1.5-6 times, after which the bubble is rolled up. There are a number of variations on this method within the skill in the art. Most references to blown polyolefin films describe methods used for polyethylene, but they are applicable to the blends described above with minor modifications within the scope of the art without undue experimentation.

For example, cooling is often advantageously modified because it is recognized in the art that polypropylene cools and crystallizes at a different rate than polyethylene.

Therefore, adjustments to the cooling parameters often provide a more stable bubble at desired exit rates.

In blow molding films, the molten mixture (melt) enters the annular die either through its bottom or through its side. The melt is forced through helical grooves around the surface of the mandrel inside the die and extruded through the hole of the die in the form of a thick-walled tube. The tube is expanded into a bubble of the desired diameter and correspondingly reduced thickness, as previously described.

Description of film production by cast film technology

In this simplest technology for the production of polymer films, the molten mixture is extruded through a slot die, fed by a (usually single screw) extruder, onto a first cooled roll, the so-called chill roll. From this roll, the already cured film is picked up by a second roll (nip roll or take-up roll) and transported to the winder after trimming the edges. Only a very limited degree of orientation is created in the film, which is determined by the ratio between die thickness and film thickness, or extrusion speed and take-up speed, respectively. Due to its technical simplicity, film casting technology is very economical and easy to operate. The films obtained as a result of this technology are characterized by good transparency and rather isotropic mechanical properties (limited rigidity, high impact strength).

To summarize, this method includes the steps:

i) pouring or spreading a solution, thermal melt or dispersion of material onto a temporary carrier;

ii) solidification of the material, and

iii) removing the cured film from the carrier surface.

Single-layer films having a thickness of 5 to 300 µm, preferably 10 to 200 µm, more preferably 20 to 150 µm, are suitable according to the invention.

Films according to the invention may be non-oriented, uniaxially or biaxially oriented.

Preferably, the films are non-oriented.

However, cast films are especially preferred, non-oriented cast films are particularly preferred.

In a particularly preferred embodiment, the polypropylene composition has a coefficient of friction (Kfp), determined in accordance with ISO 8295, corresponding to equation (I)

when cast into a film with a thickness of 50 micrometers.

In a further embodiment, the polypropylene composition has a haze of no more than 2.5%, preferably no more than 2.3%, more preferably no more than 2.1%, as determined according to ASTM D 1003 when cast into a 50 micron thick film.

Below the invention is further illustrated by means of examples.

Examples

1. 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.

MFR ₂ (230° C.) is measured according to ISO 1133 (230° C., load 2.16 kg).

Quantification of the microstructure using NMR spectroscopy

Quantitative nuclear magnetic resonance (NMR) spectroscopy was used to quantify comonomer content in polymers.

Quantitative ¹³ C{ ¹ H} NMR spectra were recorded in the dissolved state using a Bruker Avance III 400 NMR spectrometer operating at 400.15 and 100.62 MHz for ¹ H and ¹³ C, respectively. All spectra were recorded with a ¹³ C optimized 10 mm probe at 125° C. using nitrogen gas for the entire pneumatic system. 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 ), resulting in a 65 mm solution of the relaxation agent in the solvent (Singh, G., Kothari, A., Gupta, V., Polymer Testing 28 5 (2009), 475). To ensure a homogeneous solution, after the initial preparation of the sample in the thermal block, the NMR ampoule was additionally heated in a rotary oven for at least 1 hour. After insertion into the magnet, the ampoule was rotated at a frequency of 10 Hz. This setup was chosen primarily for high resolution and is quantitatively necessary for an accurate quantification of ethylene content. Standard single-pulse excitation was applied without the nuclear Overhauser effect (NOE), using an optimized tip angle, a recirculation delay of 1 s, and a two-level WALTZ 16 decoupling scheme (Zhou, Z., Kuemmerle, R., Qiu, X., Redwine, D., Cong , R., Taha, A., Baugh, D. Winniford, B., J. Mag. Reson 187 (2007) 225 Busico, V., Carbonniere, P., Cipullo, R., Pellecchia, R., Severn, J., Talarico, G., Macromol Rapid Commun. 2007, 28, 1128). A total of 6144 (6k) transitions per spectrum were obtained.

Quantitative ¹³ C { ¹ H} NMR spectra were processed, integrated, and the corresponding quantitative properties were determined from the integration using proprietary computer programs. All chemical shifts are internally assigned to the central methylene group of the ethylene block (EEE) at 30.00 ppm using the solvent chemical shift. This approach made it possible to carry out a comparable assignment even when this structural link was absent. Observed characteristic signals corresponding to the introduction of ethylene (Cheng, H. N., Macromolecules 17 (1984), 1950).

Observed characteristic signals corresponding to 2,1-erythro-regiodefects (as described in L. Resconi, L. Cavallo, A. Fait, F. Piemontesi, Chem. Rev. 2000, 100 (4), 1253, in Cheng, H. N., Macromolecules 1984, 17, 1950 and in W-J. Wang and S. Zhu, Macromolecules 2000, 33 1157), therefore, correction of the influence of regiodefects on the determined properties was required. Characteristic signals corresponding to other types of regiodefects were not observed.

The comonomer fraction was quantified using the method of Wang et al. (Wang, WJ., Zhu, S., Macromolecules 33 (2000), 1157) by integrating multiple signals over the entire spectral region in the ¹³ C{ ¹ H} spectra. This method was chosen due to its reliability and ability to take into account, if necessary, the presence of regiodefects. The regions of integration have been slightly adjusted to improve applicability over the entire range of comonomer content encountered.

For systems where only isolated ethylene was observed in PPEP sequences, the method of Wang et. al. has been modified to reduce the influence of non-zero patch integrals, which are known to be missing. This approach reduced the overestimation of ethylene content in such systems and was achieved by reducing the number of sites used to determine the absolute ethylene content to:

By using this set of plots, the corresponding integral equation becomes:

using the same notation as used in Wang et al. (Wang, W-J., Zhu, S., Macromolecules 33 (2000), 1157). The equations used to determine the absolute content of propylene have not been modified.

The mole percentage of comonomer incorporated was calculated from the molar fraction:

The mass percentage of incorporated comonomer was calculated from the molar fraction:

The distribution of comonomer sequences at the triad level was determined by the analysis method of Kakugo et al. (Kakugo, M., Naito, Y., Mizunuma, K., Miyatake, T. Macromolecules 15 (1982) 1150). This method was chosen due to its robustness and integration areas slightly adjusted to improve applicability to a wider range of comonomer content.

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

Number average molecular weight (Mn), weight average molecular weight (Mw), and polydispersity (Mw/Mn) are determined by gel permeation chromatography (GPC) according to the following method:

The weight average molecular weight Mw and polydispersity (Mw/Mn), where Mn is the number average molecular weight and Mw is the weight average molecular weight, is measured by a method based on ISO 16014-1:2003 and ISO 16014-4:2003. A Waters Alliance GPCV 2000 instrument equipped with a refractive index detector and an online viscometer was used with 3 x TSK gel columns (GMHXL-HT) from TosoHaas and 1,2,4-trichlorobenzene (TCB, stabilized 200 mg/l 2,6- di-tert-butyl-4-methyl-phenol) as a solvent at 145°C and at a constant flow rate of 1 ml/min. For each assay, 216.5 μl of sample solution was injected. The column set was calibrated using relative calibration with 19 narrow molecular weight distribution (MWD) polystyrene (PS) standards ranging from 0.5 kg/mol to 11500 kg/mol and a set of well-characterized wide polypropylene standards. All samples were prepared by dissolving 5-10 mg of polymer in 10 ml (at 160° C.) of stabilized TCB (same as mobile phase) and incubated for 3 hours with continuous shaking before sampling into the GPC instrument.

DSC analysis, melting point (T _m ) and heat of fusion (H _r ), crystallization temperature (T _cr ) and heat of crystallization (H _cr ): measured by differential scanning calorimetry (DSC) instrument TA Instrument Q2000 on samples from 5 to 7 mg. DSC is measured according to ISO 11357/part 3/method C2 in a heat/cool/heat cycle at a scan rate of 10°C/min over a temperature range of -30 to +225°C. The crystallization temperature and the heat of crystallization (H _cr ) are determined in the cooling stage, and the melting point and heat of fusion (H _f ) are determined in the second heating stage.

The glass transition temperature Tst is determined by dynamic mechanical analysis according to ISO 6721-7. The measurements are carried out in torsional vibration mode on pressed molded samples (40×10×1 mm ³ ) between -100°C and +150°C with a heating rate of 2°C/min and a frequency of 1 Hz.

Light transmission, turbidity, transparency

Light transmission, haze and clarity were determined on 50 µm cast films according to ASTM D 1003.

Sterilizability in terms of light transmission, haze and clarity was determined according to ASTM D 1003 by measuring these optical parameters after steam sterilization at 121° C. for 30 minutes on 50 µm cast films for propylene homopolymers.

Friction coefficient (Ktr)

The dynamic coefficient of friction (Ktr) as a measure of the frictional behavior of the film was determined according to ISO 8295 on film samples with a thickness of 50 μm. Immediately after the film was made, the film was stored at 23° C. and 50% relative humidity for various times: 1 day, 3 days, 7 days and 21 days. Then, a KTR measurement was carried out at 23° C. on the inside of the film roll (inside/inside friction).

2. Examples

The catalyst used in the polymerization process to produce the polypropylene homopolymer (HPP) of the examples according to the invention (IE 1, 2, 3) was prepared as follows:

Preparation of carrier MAO-silica

The steel reactor, equipped with a mechanical stirrer and filter mesh, was flushed with nitrogen, and the reactor temperature was set to 20°C. Silica DM-L-303 from AGC Si-Tech Co, pre-calcined at 600° C. (5.0 kg), was then added from the feed drum, followed by a gentle pressurization and depressurization of nitrogen using manual valves. Toluene (22 kg) was then added. The mixture was stirred for 15 minutes. Further 30 wt. A % MAO solution in toluene (9.0 kg) from Lanxess was added via the feed line to the top of the reactor over 70 minutes. The reaction mixture was then heated to 90°C and stirred at 90°C for an additional two hours. The suspension was allowed to settle and the mother liquor was filtered off. The catalyst was washed twice with toluene (22 kg) at 90° C. followed by precipitation and filtration. The reactor was cooled to 60°C and the solid was washed with heptane (22.2 kg). Finally, the MAO-treated SiO ₂ was dried at 60° under a stream of nitrogen for 2 hours and then for 5 hours under vacuum (-0.5 barg(-0.05 MPag)) with stirring. The MAO treated carrier was collected as a free flowing white powder containing 12.2% Al by weight.

Catalyst synthesis

The _C2 metallocene complex was prepared as described in WO 2019/179959 for MS-2.

In a steel reactor in a nitrogen atmosphere was added through a burette 30 wt. % MAO in toluene (0.7 kg) at 20°C. Toluene (5.4 kg) was then added with stirring. Metallocene C ₂ (93 g) was added from a metal cylinder followed by washing with 1 kg of toluene. The mixture was stirred for 60 minutes at 20°C. Then, trityltetrakis(pentafluorophenyl)borate (91 g) was added from a metal cylinder, followed by washing with 1 kg of toluene. The mixture was stirred for 1 hour at room temperature. The resulting solution was added to the stirred pellet of the MAO-silica carrier prepared as described above over 1 hour. The precipitate was left to stand for 12 hours, then dried in a stream of N ₂ at 60° C. for 2 hours and additionally for 5 hours under vacuum (-0.5 barg(-0.05 MPag)) with stirring . The dried catalyst was collected as a pink free-flowing powder containing 13.9% Al and 0.11% Zr.

Polymerization

The HLP polymerization conditions used as examples according to the invention in IE1-IE3 are shown in Table 1. Polymerization was carried out in a Borstar pilot plant, with prepolymerizer, loop and first gas phase reactors connected in series, in the presence of the catalyst described above. The resulting polymer powder was compounded with 0.1 wt. % Irganox B215, 0.05 wt. % calcium stearate on a twin screw extruder TSE 16, with a capacity of 7 kg/h and a melt temperature of 210°C. The properties measured on these products (denoted as final) are also shown in Table 1. The GLP in CE1 is a commercially available HD234CF polypropylene homopolymer from Borealis AG, made in the presence of a Ziegler-Natta catalyst, with a melting point of 164°C and an MFR _{of 2} ( 230°C) 8.0 g/10 min.

IE was prepared with a base GLP powder sample as indicated in Table 1, and different amounts of slip agent and antiblock agent were added during the mixing step. The formulations are shown in Table 2. Mixing was carried out on a ZSK 32 twin screw extruder with a capacity of 200 kg/h and a melt temperature of 210°C.

Cast films were produced on a single screw extruder with a barrel diameter of 30 mm and a slotted die of 200×0.5 mm in combination with a chill roll and a take-up roll. The temperature of the melt in the die was 260°C. The chill roll and take-up roll were maintained at 15°C. The film thickness was 50 µm and was controlled by changing the relationship between the extruder output and the stripping speed.

Additives:

Calcium stearate is Ceasit FI (CAS No. 216-472-8) manufactured by Baerlocher.

Erucic acid amide is Finawax-E (CAS No. 112-84-5) commercially available from Fine Organics.

The synthetic silica is Slobloc 45B (CAS No. 7631-86-9) commercially available from Grace.

The results are shown in Table 2 for films made from polypropylene homopolymers (IE 1-3 and CE1).

Table 2 clearly shows that the cast films according to the invention have a lower CTE already 3 days after film production and an even lower value after 7 days after film production compared to the comparative examples. At the same time, the optical properties such as haze and transparency of the films are clearly improved.

Claims (42)

1. A method for producing a film having a low dynamic coefficient of friction and good optical properties, which includes the following steps: i) propylene homopolymer (HPP) having a melting point (Tm) measured by differential scanning calorimetry (DSC) according to ISO 11357 in the range of 152 to 162°C, cold xylene soluble fraction (XCS) determined at 25 °C according to ISO 16152, equal to or less than 1.5 wt. %, and the content of 2,1-erythro-regiodefects, determined using ¹³ C-NMR spectroscopy, in the range from 0.01 to 1.00 mol. % polymerized in a multi-stage process in which a loop reactor is followed by a gas phase reactor in the presence of a metallocene catalyst system comprising: (i') metallocene catalyst complex of formula (I)

Where Mt is Hf or Zr; each X is a sigma ligand, each R ¹ , identical or different, is independently a CH ₂ -R ⁷ group, where R ⁷ is H or a linear or branched C _1-6 alkyl group, a C _3-8 cycloalkyl group, a C _6-10 aryl group, each R ² is independently a -CH=, -CY=, -CH ₂ -, -CHY- or -CY ₂ - group, where Y is a C _1-10 hydrocarbyl group and where n is 2-6, each of R ³ and R ⁴ , the same or different from each other, is independently hydrogen, a linear or branched C ₁ -C ₆ alkyl group, an OY group, or a C _7-20 arylalkyl, a C _7-20 alkylaryl group, or a C ₆ - ₂₀ aryl group, wherein at least one R ³ per phenyl group and at least one R ⁴ is not hydrogen and, optionally, two adjacent R ³ or R ⁴ groups may be part of a ring containing carbon atoms of the phenyl group with which they are connected R ⁵ is a linear or branched C ₁ -C ₆ alkyl group, a C _7-20 arylalkyl group, a C _7-20 alkylaryl group, or a C ₆ -C ₂₀ aryl group, R ⁶ is a C(R ⁸ ) ₃ group, where R ⁸ is a linear or branched C ₁ -C ₆ alkyl group, each R is independently C ₁ -C ₂₀ hydrocarbyl, C ₆ -C ₂₀ aryl, C ₇ -C ₂₀ arylalkyl, or C ₇ -C ₂₀ alkylaryl, and (ii') a cocatalyst containing a Group 13 metal compound, and ii) a polypropylene composition containing 95.0-99.9 wt. % propylene homopolymer (HPP) obtained in stage (i) together with 0.1-0.4 wt. % slip additive and 0.0-0.5 wt. % anti-blocking agent is formed into a film. 2. The method of claim 1, wherein the film is a non-oriented cast or blown film, preferably a non-oriented cast film. 3. The method according to p. 1 or 2, in which the propylene homopolymer (HPP) has a melt flow index MFR ₂ (230 ° C, 2.16 kg), determined according to ISO 1133, in the range of 4.0-20.0 g / 10 min. 4. The process according to any one of the preceding claims, wherein the propylene homopolymer (HPP) has a molecular weight distribution (MWD) equal to or less than 4.0. 5. The method according to any of the preceding claims, in which the propylene homopolymer (HPP) has a content of 2,1-erythro-regiodefects, determined using ¹³ C-NMR spectroscopy, in the range from 0.20 to 0.80 mol. % and most preferably in the range from 0.30 to 0.80 mol. %. 6. The process according to any one of the preceding claims, wherein the propylene homopolymer (HPP) has an isotactic triad fraction (mm) as determined by ¹³ C-NMR spectroscopy of at least 97.5%. 7. The method according to any one of the preceding claims, wherein the polypropylene composition has a coefficient of friction (Cfr) determined according to ISO 829 corresponding to equation (I) Ktr < 0.658 days ^-0.189 (I) when casting into a film with a thickness of 50 microns. 8. The method according to any one of the preceding claims, wherein the polypropylene composition has a haze of not more than 2.5%, as determined according to ASTM D 1003, when cast into a 50 micron thick film. 9. The method according to p. 1, in which the propylene homopolymer (HPP) is obtained by polymerization in the presence of a metallocene catalyst complex, in which Mt is Zr, each X independently represents a hydrogen atom, a halogen atom, a C _1-6 alkoxy group or an R' group, where R' represents a C _1-6 alkyl, phenyl or benzyl group, each R is independently C ₁ -C ₂₀ hydrocarbyl, C ₆ -C ₂₀ aryl, C ₇ -C ₂₀ arylalkyl, or C ₇ -C ₂₀ alkylaryl, each of R ¹ , identical or different from each other, independently represents a group CH ₂ -R ⁷ where R ⁷ represents H or a linear or branched C _1-6 alkyl group, C ₆ - ₁₀ aryl group, each R ² is independently a -CH=, -CY=, -CH ₂ -, -CHY- or -CY ₂ - group, where Y is a C _1-4 hydrocarbyl group, and where n is 3-4, each of R ³ and R ⁴ , identical or different from each other, is independently hydrogen, a linear or branched C ₁ -C ₆ alkyl group, or a C _6-20 aryl group, with at least one R ³ per phenyl group and at least one R ⁴ is not hydrogen, R ⁵ is a linear or branched C ₁ -C ₆ alkyl group or a C _6-20 aryl group, and R ⁶ is a C(R ⁸ ) ₃ group, where R ⁸ is a linear or branched C ₁ -C ₄ alkyl group. 10. The method according to claim 1 or 9, in which the propylene homopolymer (HPP) is obtained by polymerization in the presence of a metallocene catalyst complex, in which Mt is Zr, each X is independently a chlorine, benzyl or methyl group, each R is independently a C ₁ -C ₁₀ hydrocarbyl or C ₆ -C ₁₀ aryl group, both R ¹ are the same and represent a group CH ₂ -R ⁷ where R ⁷ represents H or a linear or branched C ₁ -C ₃ -alkyl group, each R ² is independently a -CH=, -CY=, -CH ₂ -, -CHY- or -CY ₂ - group, where Y is a C _1-4 hydrocarbyl group, and where n is 3-4, each of R ³ and R ⁴ , the same or different from each other, independently represents hydrogen, a linear or branched C ₁ -C ₆ -alkyl group or C _6-20 aryl groups, with at least one R ³ per phenyl group and at least one R ⁴ is not hydrogen, R ⁵ is a linear or branched C ₁ -C ₆ alkyl group or a C _6-20 aryl group, and R ⁶ represents a group C(R ⁸ ) ₃ where R ⁸ are the same and represent a C ₁ -C ₂ -alkyl group. 11. Process according to claim 1, wherein the metallocene catalyst system contains as cocatalyst (ii) alumoxane, combinations of alumoxane with Al-alkyl, boron or borate cocatalysts, and a combination of alumoxanes with boron-based co-catalysts.