RU2810068C2 - Random copolymer c2c3 - Google Patents

Abstract

FIELD: random copolymer C₂C₃.

SUBSTANCE: group of inventions is related to a C₂C₃ random copolymer with a bimodal distribution of comonomer content, exhibiting improved sealing properties due to a low seal initiation temperature (SIT) and a high peel force when determining hot tack (HTF), a method for its preparation and use. The C₂C₃ random copolymer (RACO) with a bimodal distribution of comonomer content has: (a) an ethylene content of 2.8 to 4.9 wt.%, (b) melt flow index PTR₂ (230°С/2.16 kg), measured in accordance with ISO 1133, from 1.0 to 20.0 g/10 min, (c) melting point Tm, determined by differential scanning calorimetry (DSC) in accordance with ISO 11357, from 115 to 130°C, and (d) a xylene cold soluble (XCS) fraction content of from 0.5 wt.% to less than 15.0 wt.%. Described is a method for producing the C₂C₃ random copolymer (RACO), which is obtained by polymerizing propylene and ethylene in a sequential polymerization process comprising at least two reactors connected in series in presence of a metallocene catalyst and a cocatalyst containing at least one or two compounds Group 13 metal. The use of the C₂C₃ random copolymer (RACO) to make an article, a sterilizable or sterilized article, the use of a sterilizable or sterilized article of films as a sealing layer in a multilayer film, and a flexible packaging system selected from bags or pouches for food and medicinal products, including sterilizable or sterilized film are also described.

EFFECT: C₂C₃ random copolymers (RACO) according to the invention are characterized by an advantageous combination of low seal initiation temperature (SIT), high peel force when determining hot tack and good optical properties such as low turbidity and high transparency, as well as good resistance to sterilization.

20 cl, 8 tbl, 5 ex

Description

The invention relates to a new C ₂ C ₃ random copolymer exhibiting improved sealing properties due to a low seal initiation temperature (SIT) and a high hot tack test (HTF). In addition to this, the copolymer according to the invention exhibits excellent sterilization performance, that is, maintaining a low turbidity level after sterilization. In addition, the invention relates to the production of said copolymer and its use.

Polypropylenes are suitable for many applications.

For example, polypropylene (PP) is useful in applications where sealing properties are important, such as in the food industry or pharmaceutical packaging, especially when a good combination of transparency and mechanical properties is desired. This combination is difficult to achieve if the material is to be suitable for sealable layers of multilayer films that require a good balance between seal initiation temperature (SIT) and hot tack (HTF) peel force. The combination of lower SIT and higher HTF allows the manufacturer to keep the packaging line running at higher speeds, but the overall performance of the film construction will only be satisfactory if the seal layer is sufficiently flexible, strong and transparent.

To ensure fast welding, low SIT is an advantage. By working at a lower temperature, the advantage is achieved that the workpiece being welded is not exposed to high temperatures. There are also economic advantages, since creating and maintaining lower temperatures is of course cheaper.

There are other benefits to avoiding high sealing temperatures, especially when packaging temperature-sensitive products is required.

In addition, it is also desirable to have a packaging material with satisfactory optical properties, such as low haze and/or high transparency.

In some food applications, such as sealed heat-resistant pouches (retort pouches) or in some medical applications, sterilization treatment is necessary.

The most common sterilization operations are the use of heat (steam), radiation (beta radiation, electrons, or gamma radiation), or chemicals (usually ethylene oxide). Steam sterilization is usually carried out in a temperature range of approximately 120 to 130°C. Thus, the material must have sufficient thermal stability, for example, a higher melting point than the normal steam sterilization temperature of about 120 to 130°C.

Of course, processing the polymer under the sterilization conditions specified above may degrade its final properties, especially optical properties such as transparency.

Regardless of the type of polymer, the polymer must best meet all the required end properties and must additionally be easy to process, that is, it must withstand load. However, final properties and processability properties often conflict with each other.

It is often found that an improvement in one of the desired properties is achieved at the expense of at least one of the other properties.

Several attempts have been made to solve the above problem.

EP 3064514 B1, for example, describes a composition based on a C ₂ C ₃ random copolymer for heat sealing, comprising three polymer fractions (A), (B) and (C) with different comonomer contents, the composition being obtained in the presence of a metallocene catalyst.

Compositions based on a C ₂ C ₃ random copolymer are claimed, including polymer fractions (A), (B) and (C), in which fraction (A) has a C2 (C2 A) content of 0.4 to 1.5 wt. %, fraction (B) has a C2 content (C2 B) from 3.0 to 10.0 wt. %, and fraction (C) has a C2 content (C2 C) from 7.0 to 15.0 wt. %, where the comonomer content in the polymer fractions increases from fraction (A) to fraction (C) in accordance with the inequality (C2 A) < (C2 B) < (C2 C), and the composition is characterized by (i) a total C2 content of 3, 0 to 7.0 wt. %, (ii) melt flow index PTR ₂ (230°C) from 2.0 to 15.0 g/10 min, (iii) melting temperature Tmelt from 128°C to 145°C, (iv) crystallization temperature Tcr from 85 to 110°C and (v) the content of hexane-soluble substances, determined in accordance with FDA section 177.1520, not more than 2.0 mass. %.

Such compositions have a low seal initiation temperature (SIT) but also a low hot tack (HTF) peel force. The key disadvantage of such compositions is their low resistance to sterilization, which leads to a sharp increase in turbidity after sterilization.

EP 2965908 B1 discloses a PP random copolymer with ethylene, where (a) said propylene copolymer has a C2 content of 5.3 to 9.0 wt. %, melting point Tmelting from 128 to 138°C, and the content of the fraction soluble in cold xylene (XCS) from 9.0 to 18.0 wt. %. Said propylene copolymer includes two fractions: a first propylene copolymer fraction (R-PP1) and a second propylene copolymer fraction (R-PP2), and said first propylene copolymer fraction (R-PP1) is different from said second propylene copolymer fraction (R-PP2) by ethylene content.

Such compositions already show a fairly good balance of SIT and HTF, but still have low resistance to sterilization, resulting in a sharp increase in turbidity after sterilization.

Therefore, there continues to be a need to develop materials that have improved sealing properties due to low seal initiation temperature (SIT) and high hot tack (HTF) pull-out forces, as well as excellent sterilization properties, i.e. maintaining low turbidity levels after sterilization.

The present invention is based on the discovery that the above requirements for heat sealing applications, i.e. the simultaneous presence of a low seal initiation temperature (SIT) and a high hot tack (HTF) peel force and excellent sterilization performance, can be achieved using specific structure C ₂ C ₃ statistical copolymer.

Thus, in accordance with the first aspect, the invention provides a C ₂ C ₃ random copolymer (RACO) having

(a) ethylene content from 2.5 to 5.2 wt. %;

(b) melt flow index PTR ₂ (230°C/2.16 kg), measured in accordance with ISO 1133, from 1.0 to 20.0 g/10 min;

(c) melting point Tm, determined by differential scanning calorimetry (DSC) in accordance with ISO 11357, from 115 to 135 °C;

(d) content of xylene cold soluble (XCS) fraction from 0.1 to less than 15.0 wt. %.

Preferably, the C ₂ C ₃ random copolymer (RACO) comprises two polymer fractions (RACO-1) and (RACO-2) and can be produced, preferably produced, in the presence of a metallocene catalyst. More preferably, the fraction (RACO-1) is present in an amount of from 30.0 to 70.0 wt. % and has an ethylene content of 1.5 to 5.5 wt. %, and the fraction (RACO-2) is present in an amount from 70.0 to 30.0 wt. % and has an ethylene content of 3.5 to 7.0 wt. %, while the ethylene content in the fraction (RACO-1) is lower than the ethylene content in the fraction (RACO-2).

In another aspect, the invention relates to a process for producing a C ₂ C ₃ random copolymer (RACO) described above or below, wherein the C ₂ C ₃ random copolymer (RACO) is produced by polymerizing propylene and ethylene in a sequential polymerization process comprising at least two reactors polymerization, (R1) and (R2), in which in the first polymerization reactor (R1) a first polymer fraction (RACO-1) is obtained, which is then transferred to a second polymerization reactor (R2), while in the second polymerization reactor (R2) then a second polymer fraction (RACO-2) is prepared in the presence of a first polymer fraction (RACO-1), and polymerization occurs in the presence of a specific catalyst system comprising (i) a metallocene, (ii) a cocatalyst system comprising a boron cocatalyst and an alumoxane cocatalyst, and ( iii) silica support.

In another aspect, the invention relates to sterilizable or sterilized articles, preferably sterilizable or sterilized films, comprising a C ₂ C ₃ random copolymer (RACO) described above or below, wherein the films are characterized by the following properties:

(i) seal initiation temperature (SIT) (determined as described in the experimental section) from 80°C to below 120°C,

(ii) hot tack peel force (determined as described in the experimental section, on a cast film of 50 µm thickness) from above 1.5 N to 6.0 N,

(iii) haze (measured in accordance with ASTM D1003-00 on 50 µm cast film) from 0.05% to below 2.00% and haze (determined in accordance with ASTM D 1003-00 when measured on 50 µm cast film µm) after sterilization (steam sterilization at 121°C for 30 min) from 0.30% to below 7.00%, and

(iv) transparency (determined in accordance with ASTM D1003-00 on 50 µm cast film) of at least 85.0% to 100.0% and transparency (determined in accordance with ASTM D1003-00 on 50 µm cast film ) after sterilization (steam sterilization at 121°C for 30 minutes) from at least 75.0% to 100.0%.

In yet another aspect, the invention relates to the use of films according to the invention as a sealable layer in a multilayer film, which can be produced either by co-extrusion or by lamination.

The invention is described in more detail below.

C ₂ C ₃ random copolymer (RACO)

The C ₂ C ₃ random copolymer (RACO) according to the invention is a random copolymer of propylene and ethylene as a comonomer.

The C ₂ C ₃ random copolymer (RACO) can be, and preferably is, produced in the presence of a metallocene catalyst.

The C ₂ C ₃ random copolymer (RACO) of this invention has a moderate to low ethylene comonomer content.

Accordingly, C ₂ C ₃ random copolymer (RACO) has an ethylene content of 2.5 to 5.2 wt. %, preferably from 2.7 to 5.0 wt. %, more preferably from 2.8 to 4.9 wt. %, and even more preferably from 3.0 to 4.8 wt. %.

C ₂ C ₃ random copolymer (RACO) has a melt flow index PTR2 (230°C), measured in accordance with ISO 1133, from 1.0 to 20.0 g/10 min, preferably from 2.0 to 15.0 g /10 min, more preferably from 3.0 to 12.0 g/10 min and even more preferably from 5.0 to 10.0 g/10 min.

In some embodiments, the C ₂ C ₃ random copolymer (RACO) has a melt flow index MFR ₂ (230°C), measured in accordance with ISO 1133, of at least 7.0 g/10 min. In these embodiments, the upper limit of the melt flow rate of PTR ₂ (230°C) may be up to 20.0 g/10 min, preferably up to 15.0 g/10 min, more preferably up to 12.0 g/10 min, and even more preferably up to 10.0 g/10 min.

In addition, C ₂ C ₃ random copolymer (RACO) can be determined by the xylene cold soluble content (XCS) determined at 25°C in accordance with ISO 16152; 2005. Accordingly, C ₂ C ₃ random copolymer (RACO) is characterized by a xylene cold soluble (XCS) content of 0.1 wt. % to less than 15.0 wt. %, for example from 0.5 to less than 15.0 wt. %.

Preferably, the C ₂ C ₃ random copolymer (RACO) has a xylene cold soluble (XCS) content of 2.0 to 14.0 wt. % and most preferably from 5.0 to less than 13.0 wt. %.

In addition, C ₂ C ₃ random copolymer (RACO) can be defined by a melting point (Tm) measured by differential scanning calorimetry (DSC) in accordance with ISO 11357. Accordingly, C ₂ C ₃ random copolymer (RACO) has a melting point Tm from 115°C to 135°C, preferably from 118°C to 134°C, and more preferably from 120°C to 133°C.

In some embodiments, the C ₂ C ₃ random copolymer (RACO) has a melting point (Mp) of 115°C to 130°C, preferably 118°C to 128°C, and more preferably 120°C to 126°C.

To facilitate processing, especially film processing, it is also desirable that the C ₂ C ₃ random copolymer (RACO) of the invention has a suitable crystallization temperature even in the absence of any nucleating agents. Therefore, preferably the C ₂ C ₃ random copolymer (RACO) has a crystallization temperature Tcr, determined by DSC (differential scanning calorimetry) in accordance with ISO 11357, from 75°C to 110°C, more preferably from 80°C to 105°C, for example, from 82°C to 100°C.

The C ₂ C ₃ random copolymer (RACO) preferably also has a flexural modulus, determined in accordance with ISO 178 on injection molded specimens, from 500 to below 1000 MPa, preferably from 550 to 900 MPa, more preferably from 600 to 900 MPa.

Thus, in the first embodiment of the invention there is provided a C ₂ C ₃ random copolymer (RACO) having

(a) ethylene content from 2.5 to 5.2 wt. %;

(b) melt flow index PTR ₂ (230°C), measured in accordance with ISO 1133, from 1.0 to 20.0 g/10 min;

(c) melting point (Tm), determined by DSC in accordance with ISO 11357, from 115°C to 135°C;

(d) content of the cold xylene soluble fraction (XCS), from 0.1 wt. % to less than 15.0 wt. %;

(e) crystallization temperature Tcr, determined by DSC (differential scanning calorimetry) in accordance with ISO 11357, from 75°C to 110°C, preferably from 80°C to 105°C, and

(f) flexural modulus, determined in accordance with ISO 178 on injection molded specimens, from 500 to below 1000 MPa, preferably from 550 to 900 MPa.

The C ₂ C ₃ random copolymer (RACO) is preferably multimodal, eg bimodal, in terms of comonomer content and includes, preferably consists of, polymer fractions (RACO-1) and (RACO-2).

Thus, C ₂ C ₃ random copolymer (RACO) includes from 30.0 to 70.0 wt. % polymer fraction (RACO-1) having

(i) ethylene content from 1.5 to 5.5 wt. % And

(ii) melt flow index PTR ₂ (230°C/2.16 kg), measured in accordance with ISO 1133, from 4.0 to 15.0 g/10 min, and

from 70.0 to 30.0 wt. % polymer fraction (RACO-2) having

(i) ethylene content from 3.5 to 7.0 wt. % And

(ii) melt flow index PTR ₂ (230°C/2.16 kg), measured in accordance with ISO 1133, from 4.0 to 12.0 g/10 min,

Moreover, the ethylene content in the polymer fraction (RACO-1) is lower than the ethylene content in the polymer fraction (RACO-2).

Preferably, the C ₂ C ₃ random copolymer (RACO) includes from 40.0 to 70.0 wt. % polymer fraction (RACO-1) and from 30.0 to 60.0 wt. % polymer fraction (RACO-2).

More preferably, the C ₂ C ₃ random copolymer (RACO) includes from 45.0 to 65.0 wt. % polymer fraction (RACO-1) and from 35.0 to 55.0 wt. % polymer fraction (RACO-2).

The polymer fraction (RACO-1) preferably has an ethylene content of 2.8 to 5.0 wt. % and more preferably from 3.0 to 4.8 wt. %.

The melt flow index of PTR ₂ (230°C/2.16 kg), measured in accordance with ISO 1133, of the polymer fraction (RACO-1) is preferably from 5.0 to 12.0 g/10 min.

The polymer fraction (RACO-2) preferably has an ethylene content of 3.7 to 6.5 wt. % and more preferably from 3.8 to 5.5 wt. %.

The melt flow index of PTR ₂ (230°C/2.16 kg), measured in accordance with ISO 1133, of the polymer fraction (RACO-2) is preferably from 5.0 to 10.0 g/10 min.

Thus, C ₂ C ₃ random copolymer (RACO) is preferably produced by polymerizing propylene and ethylene through a sequential polymerization process comprising at least two reactors in series, in the presence of a metallocene catalyst.

Thus, the C ₂ C ₃ random copolymer (RACO) is preferably produced in a sequential polymerization process comprising at least two polymerization reactors (R1) and (R2), wherein the first polymerization reactor (R1) produces a first polymer fraction (RACO- 1), which is then transferred to the second polymerization reactor (R2). In a second polymerization reactor (R2), a second polymer fraction (RACO-2) is then produced in the presence of a first polymer fraction (RACO-1).

Polymerization processes suitable for the production of C ₂ C ₃ random copolymer (RACO) generally involve at least two polymerization stages, and each stage can be carried out in solution, suspension, fluidized bed, bulk or gas phase.

The term "polymerization reactor" should indicate that the main polymerization is taking place. Thus, in the case where the process consists of one or two polymerization reactors, this definition does not exclude the option that the entire system includes, for example, a pre-polymerization step in a pre-polymerization reactor. The term “consists of” is a closed formulation only in relation to the main polymerization reactors.

The term "sequential polymerization process" indicates that the C ₂ C ₃ random copolymer (RACO) is produced in at least two reactors connected in series. Accordingly, such a polymerization system includes at least a first polymerization reactor (R1) and a second polymerization reactor (R2), and optionally a third polymerization reactor (R3).

The first polymerization reactor (R1) is preferably a slurry reactor and can be any continuous or simple stirred bulk reactor or loop reactor for bulk or slurry operation. "Bulk" means polymerization in a reaction medium that contains at least 60% (w/w) monomer. According to the invention, the slurry reactor is preferably a loop reactor (for bulk operation).

The second polymerization reactor (R2) and possible third polymerization reactor (R3) are preferably gas-phase reactors (GPR), that is, the first gas-phase reactor (GPR1) and the second gas-phase reactor (GPR2). The gas phase reactor (GPR) according to this invention is preferably a fluidized bed reactor, a fast fluidized bed reactor or a fixed bed reactor, or any combination thereof.

A preferred multi-stage process is, for example, the "loop-gas-phase" process developed by Borealis (known as BORSTAR**® technology), described for example in patent literature, for example in EP 0887379, 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® process developed by Basell.

Preferably, in the proposed method for producing C ₂ C ₃ random copolymer defined above, the conditions in the first reactor (R1), that is, in a slurry reactor (SR), such as a loop reactor (LR), in step (a) may be as follows:

- the temperature is from 40 to 110°C, preferably from 60 to 100°C, preferably from 65 to 95°C,

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

- to regulate the molecular weight, hydrogen can be added in a manner known in the art.

The reaction mixture from the first reactor (R1) is then transferred to a second reactor (R2), i.e. a gas phase reactor (GPR1), where the conditions are preferably as follows:

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

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

- to regulate the molecular weight, hydrogen can be added in a manner known in the art.

Preferably, the C ₂ C ₃ random copolymer (RACO) according to this invention is produced in the presence of a metallocene catalyst.

Thus, C ₂ C ₃ random copolymer (RACO) is obtained by a method including the following operations:

a) polymerization in the first reactor (R1) of propylene and ethylene to obtain the polymer fraction (RACO-1) C ₂ C ₃ random copolymer (RACO),

b) transferring said polymer fraction (RACO-1) and unreacted comonomers from the first reactor to the second reactor (R2),

c) feeding said second reactor (R2) propylene and ethylene,

d) polymerization in said second reactor (R2) and in the presence of said polymer fraction (RACO-1) of propylene and ethylene to obtain a polymer fraction (RACO-2),

wherein said polymer fraction (RACO-1) and said polymer fraction (RACO-2) form a C2C3 random copolymer (RACO) as described above,

wherein the polymerization is carried out in the presence of a metallocene catalyst, including (a) a complex of formula (I):

(I)

Where

M represents zirconium or hafnium; each X represents a sigma ligand;

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, C ₁ -C ₂₀ -hydrocarbyl, tri(C ₁ -C ₂₀ -alkyl)silyl, C ₆ -C ₂₀ -aryl, C ₇ -C ₂₀ -arylalkyl or C ₇ - C ₂₀ -alkylaryl;

R ² and R ² ' are each independently a C ₁ -C ₂₀ hydrocarbyl radical, possibly containing one or more heteroatoms from groups 14-16;

R ⁵ ' represents a C _1-20 hydrocarbyl group containing one or more heteroatoms from groups 14-16, optionally substituted with one or more halogen atoms;

R ⁶ and R ⁶ ' each independently represent hydrogen or a C _1-20 hydrocarbyl group, optionally containing one or more heteroatoms from groups 14-16, where R ⁶ ' preferably represents a tertiary alkyl group;

R ⁷ represents hydrogen or a C _1-20 hydrocarbyl group, optionally containing one or more heteroatoms from groups 14-16; R ⁷ ' represents hydrogen;

Ar and Ar' each independently represent an aryl or heteroaryl group having up to 20 carbon atoms, optionally substituted by one or more R ¹ groups;

each R ¹ represents a C _1-20 hydrocarbyl group, or two R ¹ groups on adjacent carbon atoms, taken together, can form a fused 5- or 6-membered non-aromatic ring with an Ar or Ar' group, where said ring itself is possibly substituted by one or more R ⁴ groups;

each R ⁴ represents a C _1-20 hydrocarbyl group;

and (ii) a cocatalyst comprising at least one or two Group 13 metal compounds, for example an Al and/or boron compound.

More preferably, a cocatalyst system is used comprising a boron-containing cocatalyst, such as a borate, and an aluminoxane cocatalyst.

Even more preferably, the catalyst is supported on a silica support.

Catalyst

The catalyst used in the method according to the invention is in the form of solid particles. It can be supported on a conventional carrier such as silica known to one skilled in the art. Preferred complexes for use in the invention are those having formula (II') or (II)

Where

M represents zirconium or hafnium;

each X represents a sigma ligand, preferably each X independently represents a hydrogen atom, a halogen atom, a C _1-6 alkoxy group, a C _1-6 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, C _1-20 alkyl, C _3-10 cycloalkyl, tri(C _1-20 -alkyl)silyl, C _6-20 -aryl, C _7-20 arylalkyl or C _{7- 20} alkylaryl;

each R ² or R ² ' represents a C _1-10 alkyl group;

R ⁵ ' represents a C _1-10 alkyl group or a Z'R ³ 'group;

R ⁶ represents hydrogen or a C _1-10 alkyl group;

R ⁶ ' represents a C _1-10 alkyl group or a C _6-10 aryl group; preferably a tertiary alkyl group;

R ⁷ represents hydrogen, a C _1-6 alkyl group or a ZR ³ group;

R ⁷ ' represents hydrogen;

Z and Z' are independently O or S;

R ³ ' represents a C _1-10 alkyl group, or a C _6-10 aryl group, optionally substituted by one or more halogen groups;

R ³ represents a C _1-10 alkyl group;

each n is independently between 0 and 4, such as 0, 1 or 2;

and each R ¹ independently represents a C _1-20 hydrocarbyl group, for example a C _1-10 alkyl group.

Other preferred complexes for use in the invention are those of formula (III') or (III):

Where

M represents zirconium or hafnium;

each X represents a sigma ligand, preferably each X independently represents a hydrogen atom, a halogen atom, a C _1-6 alkoxy group, a C _1-6 alkyl, phenyl or benzyl group;

L represents a divalent bridge selected from -R' ₂ C- or -R' ₂ Si-, where each R' independently represents a hydrogen atom, C _1-20 alkyl or C _3-10 cycloalkyl;

R ⁶ represents hydrogen or a C _1-10 alkyl group;

R ⁶ ' represents a C _1-10 alkyl group or a C _6-10 aryl group; preferably a tertiary alkyl group;

R ⁷ represents hydrogen, C _1-6 alkyl or OC _1-6 alkyl;

Z represents O or S;

R ³ ' represents a C _1-10 alkyl group, or a C _6-10 aryl group, optionally substituted by one or more halogen groups;

n is independently from 0 to 4, such as 0, 1 or 2; and each R ¹ independently represents a C _1-10 alkyl group.

Other preferred complexes for use in the invention are those of formula (IV) or (IV):

Where

M represents zirconium or hafnium;

each X represents a sigma ligand, preferably each X independently represents a hydrogen atom, a halogen atom, a C _1-6 alkoxy group, a C _1-6 alkyl, phenyl or benzyl group;

each R' independently represents a hydrogen atom, C _1-20 alkyl or C _3-7 cycloalkyl;

R ⁶ represents hydrogen or a C _1-10 alkyl group;

R ⁶ ' represents a C _1-10 alkyl group or a C _6-10 aryl group, preferably a tertiary alkyl group;

R ⁷ represents hydrogen, C _1-6 alkyl or OS _1-6 alkyl;

Z represents O or S;

R ³ ' represents a C _1-10 alkyl group, or a C _6-10 aryl group, optionally substituted by one or more halogen groups; n is independently 0, 1 or 2; And

each R ¹ independently represents a C _3-8 alkyl group.

Particularly preferably, the complex for use in the invention is a complex of formula (V') or (V):

Where

each X independently represents a hydrogen atom, a halogen atom, a C _1-6 alkoxy group, a C _1-6 alkyl, phenyl or benzyl group;

R' independently represents C _1-6 alkyl or C _3-10 cycloalkyl;

R ¹ independently represents C _3-8 alkyl;

R ⁶ represents hydrogen or a C _3-8 alkyl group;

R ⁶ ' represents a C _3-8 alkyl group or a C _6-10 aryl group, preferably a tertiary C _4-8 alkyl group;

R ³ ' represents a C _1-6 alkyl group, or a C _6-10 aryl group, optionally substituted by one or more halogen groups; And

n is independently 0, 1 or 2.

Specific compounds of the invention include:

Most preferably, rac-anti-Me ₂ Si(2-Me-4-(p-tBuPh)-Ind)(2-Me-4-Ph-5-OMe-6-tBu-Ind)ZrCl ₂ is used.

The ligands needed to form the complexes and thus the catalysts of the invention can be synthesized by any method, and one skilled in organic chemistry can develop various synthesis protocols to obtain the required ligand materials. Synthesis protocols in general can also be found in WO 2002/02576, WO 2011/135004, WO 2012/084961, WO 2012/001052, WO 2011/076780, WO 2013/007650, WO 2015/158790 and WO 2018/ 122134. The examples section also provides guidance sufficient for a specialist.

Cocatalyst

To form active catalyst species, it is generally necessary to use a cocatalyst, as is well known in the art. Suitable cocatalysts for use in this invention include one or more Group 13 metal compounds, such as organoaluminum compounds or boron-containing cocatalysts or combinations thereof, which are used to activate metallocene catalysts.

In a preferred embodiment of the present invention, a co-catalyst system is used comprising a boron-containing co-catalyst, for example a borate co-catalyst, and an aluminoxane co-catalyst.

Thus, the single site metal polymerization catalyst system used in the invention may comprise (i) a complex as described above and an alumoxane cocatalyst.

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

where n is from 6 to 20, and R has the values given below.

Alumoxanes are formed by partial hydrolysis of organoaluminum compounds, for example those having the formula AlR ₃ , AlR ₂ Y and Al ₂ R ₃ Y ₃ , where R can be, for example, C ₁ -C ₁₀ -alkyl, preferably C ₁ -C ₅ -alkyl , or C ₃ -C ₁₀ -cycloalkyl, C ₇ -C ₁₂ -arylalkyl or -alkylaryl and/or phenyl or naphthyl, and where Y may be hydrogen, halogen, preferably chlorine or bromine, or C ₁ -C ₁₀ -alkoxy -group, preferably a methoxy group or an ethoxy group. The resulting oxygen-containing alumoxanes are generally not pure compounds, but are oligomers of formula (II).

A preferred alumoxane is methylaluminoxane (MAO).

Since the alumoxanes used according to the invention as cocatalysts are not pure compounds due to the method of their preparation, the molar concentration of the alumoxane solutions is calculated here on the basis of the aluminum contained therein.

According to the invention, it is also possible to use a boron-containing cocatalyst. Suitable boron-containing cocatalysts include those of formula (III)

where Y are the same or different, and represent a hydrogen atom, an alkyl group of 1-20 carbon atoms, an aryl group of 6-15 carbon atoms, alkylaryl, arylalkyl, haloalkyl or haloaryl, each of which has from 1 to 10 carbon atoms in alkyl radical and 6-20 carbon atoms in an aryl radical, or fluorine, chlorine, bromine or iodine. Preferred examples of Y are fluorine, trifluoromethyl, aromatic fluorinated groups such as p-fluorophenyl, 3,5-difluorophenyl, pentafluorophenyl, 3,4,5-trifluorophenyl, and 3,5-di(trifluoromethyl)phenyl. Preferred options are trifluoroborane, tris(4-fluorophenyl)borane, tris(3,5-difluorophenyl)borane, tris(4-fluoromethylphenyl)borane, tris(2,4,6-trifluorophenyl)borane, tris(pentafluorophenyl)borane, tris (3,5-difluorophenyl)borane and/or tris(3,4,5-trifluorophenyl)borane.

Particularly preferred is tris(pentafluorophenyl)borane.

However, it is preferable to use borates, that is, borate-containing compounds, as the boron-containing cocatalyst.

These compounds generally contain an anion of the formula

where Z is an optionally substituted phenyl derivative, said substituent being a halogen-C _1-6 alkyl or halogen group. Preferred options are fluoro or trifluoromethyl. Most preferably, the phenyl group is perfluorinated.

Such ionic cocatalysts preferably contain a weakly coordinating anion such as tetrakis(pentafluorophenyl)borate or tetrakis(3,5-di(trifluoromethyl)phenyl)borate. Suitable counterions are 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:

tributylammonium tetra(pentafluorophenyl)borate, tributylammonium tetra(trifluoromethylphenyl)borate, tributylammonium tetra(4-

fluorophenyl)borate, N,N-dimethylcyclohexylammonium tetrakis(pentafluorophenyl)borate, N,N-dimethylbenzylammonium tetrakis(pentafluorophenyl)borate, N,N-dimethylanilininiumtetrakis(pentafluorophenyl)borate, N,N-di(propyl)ammonium tetrakis(pentafluorophenyl)borate, di( cyclohexyl)ammonium tetrakis(pentafluorophenyl)borate, triphenylcarbenium tetrakis(pentafluorophenyl)borate or ferrocenium tetrakis(pentafluorophenyl)borate.

Preferred are triphenyl carbenium tetrakis(pentafluorophenyl)borate, N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate, N,N-dimethylcyclohexylammonium tetrakis(pentafluorophenyl)borate or N,N-dimethylbenzylammonium tetrakis(pentafluorophenyl)borate.

According to the invention, it is particularly preferred to use an alumoxane co-catalyst, such as MAO, together with a boron-containing co-catalyst, such as a borate co-catalyst.

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

Preferably, the amount of cocatalyst is selected to achieve the molar ratios indicated below.

The molar ratio of the amount of boron (B) supplied to the metal ion (M) (preferably zirconium) in the metallocene, boron/M, can be from 0.1:1 to 10:1 mol/mol, preferably from 0.3:1 to 7: 1 mol/mol, especially 0.3:1 to 5:1 mol/mol.

Even more preferably, the molar ratio of the supplied amount of boron (B) to metal ion (M) (preferably zirconium) in the boron/M metallocene is from 0.3:1 to 3:1.

The molar ratio of Al from alumoxane to metal ion (M) (preferably zirconium) in the metallocene, Al/M may be from 1:1 to 2000:1 mol/mol, preferably from 10:1 to 1000:1 mol/mol, or more preferably from 50:1 to 600:1 mol/mol.

Catalytic system

The catalyst system used to produce the C ₂ C ₃ random copolymers of the invention is ideally provided in the form of solid particles supported on an external support.

The particulate carrier material used is silica or a mixed oxide such as aluminosilicate. Preferably, silica is used as the carrier. One skilled in the art will know the operations required to apply the metallocene catalyst.

Particularly preferably, the support is a porous material so that the complex can be loaded into the pores of the support in the form of solid particles, for example using a process similar to those described in WO 94/14856, WO 95/12622 and WO 2006/097497.

The average particle size of the silica carrier can typically range from 10 to 100 microns. However, it has turned out that particular advantages can be obtained if the carrier has an average particle size of from 15 to 80 μm, preferably from 18 to 50 μm.

The average pore size of the silica carrier can be from 10 to 100 nm, and the pore volume from 1 to 3 ml/g.

Examples of suitable carrier materials are, for example, ES747JR manufactured and sold by PQ Corporation, Sylopol 948 manufactured and sold by Grace, or SUNSPERA DM-L-303 silica manufactured by AGC Si-Tech Co. The supports may optionally be calcined before use in catalyst preparation in order to achieve an optimal content of silanol groups.

The use of such media is common in the art.

Supplements

The C ₂ C ₃ random copolymer (RACO) of the invention may optionally include one or more additives in a total amount of from 0.1 to 5.0 wt. % based on the copolymer, selected from the group consisting of slip agents, anti-adhesives, UV stabilizers, antistatic agents, alpha-nucleating agents and antioxidants. The number of such additives and the amount of C ₂ C ₃ random copolymer (RACO) according to the invention totals 100.0 wt. %.

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

Friction-reducing additives are also widely known in the art. The reducing additives migrate to the surface and act as lubricants for the polymer against the polymer and for the polymer against the metal rolls, resulting in a reduced coefficient of friction (CoF). Examples are fatty acid amides such as erucamide (CAS No. 112-84-5), oleamide (CAS No. 301-02-0), stearamide (CAS No. 124-26-5) or combinations thereof.

Examples of antioxidants that are 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)™ from Clariant, or Irgafos 168 (FF)™ from 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 antioxidant mixtures.

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, CAS No. 11097-59-9), lactates and lactylates, and calcium stearate (CAS No. 1592-23-0) and zinc stearate (CAS No. 557-05-1).

Commonly known release agents are natural silica such as diatomaceous earth (eg, CAS No. 60676-86-0 (SuperFloss™), CAS No. 60676-86-0 (SuperFloss E™), or CAS No. 60676-86- 0 (Celite 499™)), synthetic silica (such as CAS No. 7631-86-9, CAS No. 7631-86-9, CAS No. 7631-86-9, CAS No. 7631-86-9, CAS No. 7631-86-9, CAS No. 7631-86-9, CAS No. 112926-00-8, CAS No. 7631-86-9 or CAS No. 7631-86-9), silicates (such as aluminum silicate (Kaolin, 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 silicate calcium CAS No. 1344-95-2), synthetic zeolites (such as sodium calcium aluminosilicate hydrate CAS No. 1344-01-0, CAS No. 1344-01-0, or sodium calcium aluminosilicate hydrate CAS No. 1344- 01-0).

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) can also be added; a mixture of aluminum hydroxybis[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 at levels of 100-1000 ppm for each individual component.

Preferably, at least an antioxidant is added.

Product

The invention relates not only to the C ₂ C ₃ random copolymer (RACO) itself, but also to its use and to articles comprising the C ₂ C ₃ random copolymer according to the invention.

The C ₂ C ₃ random copolymer (RACO) according to the invention can be converted into a final product, that is, an article, using conventional processing methods such as injection molding, direct compression, blow molding (extrusion or injection stretch blow molding) , extrusion (extrusion of films, sheets, pipes, tubes, profiles), film blowing, thermoforming and the like. Preferably, the products are packaging containers made by injection molding, blow molding or thermoforming, or packaging films made by extruding films.

Thus, the C ₂ C ₃ random copolymer (RACO) according to the invention is suitable for the manufacture of various products such as films (cast films and blown films) for flexible packaging systems such as bags or pouches for food products and pharmaceutical packaging , or medical products in general, as well as molded products.

Articles comprising the C ₂ C ₃ random copolymer (RACO) of the invention have sufficient heat resistance to permit sterilization processing.

Thus, the invention also provides a sterilizable or sterilized article, preferably a sterilizable or sterilized film, such as a sterilizable or sterilized cast or blown film.

Such films can be steam sterilized in a temperature range of about 120 to 130°C.

In one embodiment, the invention relates to an article that is a non-oriented monolayer film comprising a C ₂ C ₃ random copolymer (RACO) according to the invention. Accordingly, the invention also relates to an article that is a non-oriented single-layer film, such as a cast film or a blown film, for example an air-cooled blown film, comprising at least 70 wt. %, preferably including at least 80 wt. %, even more preferably including at least 85 wt. % C ₂ C ₃ random copolymer (RACO) according to the invention.

The above composition is suitable for the production of both blown films and cast films. Preferred films are cast films.

According to the invention, suitable single-layer films have a thickness of 5 to 300 µm, preferably 10 to 200 µm, more preferably 20 to 150 µm.

Films, preferably cast films, comprising C ₂ C ₃ random copolymer (RACO) according to the invention have the following beneficial properties (i)-(iv):

(i) the films have a seal initiation temperature (SIT), determined on a cast film of 50 μm thickness, as described in the experimental section, from 80°C to below 120°C.

Preferably, the films have a seal initiation temperature (SIT) of 80 to 115°C, preferably 85 to less than 112°C, for example 90 to less than 111°C.

The low SIT of such a film is combined with (ii) high hot tack (HTF) peel forces determined on 50 µm thick cast film (as described in the experimental section) from above 1.5 N to 6.0 N.

Preferably, the films have a high hot tack strength of 1.6 to 6.0 N, more preferably 1.6 to 5.0 N.

The films have (iii) a haze, determined in accordance with ASTM D 1003-00 on a 50 µm cast film, below 2.00%, preferably below 1.50%, and more preferably below 1.00%.

An acceptable lower limit is, for example, 0.05%. Thus, acceptable ranges are from 0.05% to below 2.00%, preferably from 0.10% to below 1.50%, and more preferably from 0.15% to below 1.00%.

In addition, the films have a haze value, determined in accordance with ASTM D 1003-00 on a cast film of 50 µm thickness, after steam sterilization at 121°C for 30 minutes, below 7.00%, preferably below 5.00%, or more preferably below 4.00%.

An acceptable lower limit is, for example, 0.30%. Thus, acceptable ranges are from 0.30% to below 7.00%, preferably from 0.50% to below 5.00%, and more preferably from 0.80% to below 4.00%.

In addition, the films have (iv) a transparency, as determined in accordance with ASTM D1003-00 on 50 μm thick cast films, of at least 85.0% and up to 100%, preferably at least 90.0%, and more preferably at least at least 95.0%.

Transparency, determined in accordance with ASTM D1003-00 on 50 µm thick cast films, after sterilization (steam sterilization at 121°C for 30 minutes) is at least 75.0% and up to 98.0%, preferably at least 80.0% and more preferably at least 85.0%.

Thus, according to another embodiment, the invention also relates to sterilizable or sterilized articles, wherein the articles are films, and these films are characterized by the following properties:

(i) seal initiation temperature (SIT), determined as described in the experimental section, in the range from 80°C to below 120°C,

(ii) hot tack pull force, determined as described in the experimental section on a 50 µm thick cast film, from above 1.5 N to 6.0 N,

(iii) haze determined in accordance with ASTM D 1003-00 on 50 µm cast film from 0.05% to below 2.00% and haze determined in accordance with ASTM D 1003-00 on 50 µm cast film , after sterilization (steam sterilization at 121°C for 30 minutes) from 0.30% to below 7.00%, and

(iv) transparency determined in accordance with ASTM D1003-00 on 50 µm cast films of at least 85.0% and up to 100%, and transparency determined in accordance with ASTM D1003-00 on 50 µm cast films, after sterilization (steam sterilization at 121°C for 30 minutes) at least 75.0% and up to 98.0%.

In addition, such films should preferably have a tensile modulus determined in accordance with ISO 527-3 at 23°C on cast films of 50 µm thickness in the longitudinal (machine) direction (MD) as well as in the transverse direction from 300 to 600 MPa, more preferably 320 to 550 MPa, for example 350 to 500 MPa.

In another embodiment of the invention, the films have a resistance coefficient (R-factor) according to the formula

from more than 3000 to 6000.

Preferably, the resistance factor (R-factor) is greater than 3200 to 5500, more preferably greater than 3400 to 5000.

The resistance factor (R-factor) of the films of the invention is determined by multiplying the tensile modulus (MD) by the hot tack (HTF) peel force and calculating the ratio of this product to the haze determined before sterilization.

Preferably, the films described above include a C ₂ C ₃ random copolymer (RACO) according to the invention.

The multilayer film structure comprising at least one layer comprising a C ₂ C ₃ random copolymer (RACO) according to the invention is preferably produced by multilayer coextrusion followed by film casting or film blowing. In this case, at least one of the outer layers of said multilayer film structure serving as the sealable layer(s) comprises a C ₂ C ₃ random copolymer according to the invention as defined above. The multilayer film structure according to the invention preferably has a thickness of 30 to 500 μm, preferably 50 to 400 μm, for example 60 to 300 μm. The sealable layer(s) comprising the C ₂ C ₃ random copolymer (RACO) according to the invention preferably has a thickness of 3 to 50 μm, more preferably 5 to 30 μm, for example 8 to 25 μm.

Films and/or multilayer film structures according to the invention are preferably used for flexible packaging systems such as bags or pouches for food and pharmaceutical packaging or medical devices in general.

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

Measurement methods

Calculation of comonomer content in the second polymer fraction (RACO-2):

Where

w(A-1) - mass fraction (in mass %) of the first polymer fraction (RACO-1),

w(A-2) - mass fraction (in mass %) of the second polymer fraction (RACO-2),

C(A-1) - comonomer content (in mass %) in the first polymer fraction (RACO-1),

C(A) - comonomer content (in mass %) in C ₂ C ₃ statistical copolymer (RACO),

C(A-2) - calculated comonomer content (in mass %) in the second polymer fraction (RACO-2).

Calculation of the melt flow index PTR ₂ (230°C) of the polymer fraction (RACO-2):

Where

w(A1) - mass fraction (in mass %) of the polymer fraction RACO-1

w(A2) - mass fraction (in mass %) of the polymer fraction RACO-2,

PTR(A1) - melt flow index PTR ₂ (230°C) [g/10 min] of the RACO-1 polymer fraction,

PTR(A) - melt flow index PTR ₂ (230°C) [g/10 min] C ₂ C ₃ statistical copolymer (RACO),

PTR(A2) - calculated melt flow rate PTR ₂ (230°C) [g/10 min] of the RACO-2 polymer fraction.

MFR ₂ (230°C) is measured in accordance with ISO 1133 (230°C, load 2.16 kg).

Quantification of microstructure by NMR spectroscopy Quantitative nuclear magnetic resonance (NMR) spectroscopy was further used to quantify comonomer content and comonomer sequence distribution in the polymers. Quantitative ¹³ C { ¹ H} NMR spectra were recorded in solutions using a Bruker Advance III 400 NMR spectrometer operating at a frequency of 400.15 and 100.62 MHz for ¹ H and ¹³ C, respectively. All spectra were recorded using a ¹³ C optimized extended 10 mm temperature probe at 125 C using nitrogen gas for the entire pneumatic system. Approximately 200 mg of material was dissolved in 3 ml of 1,2-tetrachloroethane-d ₂ (TCE-d ₂ ) along with chromium(III) acetylacetonate (Cr(acac) ₃ ) to obtain a 65 mM solution of the relaxant in the solvent (Singh, G., Kothari, A., Gupta, V., Polymer Testing 28 5 (2009), 475). To ensure a homogeneous solution, after initial sample preparation in the heat block, the NMR ampoule was further heated in a rotary oven for at least 1 hour. After insertion into the magnet, the ampoule was rotated at a speed of 10 Hz. This setup was chosen primarily for high resolution and was quantitatively necessary for accurate ethylene quantification. Standard single-pulse excitation without NOE (nuclear Overhauser effect) was used using an optimized apex angle, a 1 s recirculation delay, and a WALTZ16 two-level decoupling circuit (Zhou, Z., Kuemmerle, R., Qiu, X., Redwine, D., Cong, R., Taha, A., Baugh, D. Winniford, V., 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 (6 k) transitions were obtained in the spectrum.

Quantitative ^13C { ^1H } NMR spectra were processed, integrated, and corresponding quantitative properties were determined from integrals using proprietary computer programs. All chemical shifts were indirectly assigned to the central methylene group of the ethylene block (EEE) at 30.00 ppm. using solvent chemical shift. This approach made it possible to obtain comparable assignments even if this structural link was missing. Characteristic signals consistent with the incorporation of ethylene were observed (Cheng, N.N., Macromolecules 17(1984), 1950).

In the presence of characteristic signals corresponding to the observed 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 W-J. Wang and S. Zhu, Macromolecules 2000, 33 1157) required correction to take into account the influence of regional defects on the determined properties. No characteristic signals corresponding to other types of regional defects were observed.

The comonomer fraction was quantified using the method of Wang et. al. (Wang, W. J., Zhu, S., Macromolecules 33 (2000), 1157) by integrating multiple signals across 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 the presence of regional defects when necessary. The integration regions have been slightly adjusted to increase applicability over the entire detection range of comonomer content.

For systems where only isolated ethylene in PPEPP sequences was observed, the method of Wang et. al. was modified to reduce the influence of non-zero integrals for sites not known to be present. This approach reduced the overestimation of ethylene content for such systems and was achieved by reducing the number of sites used to determine absolute ethylene content to the following:

E=0.5(Sββ+Sβγ+Sβδ+0.5(Sαβ+Sαγ))

Thanks to the use of this set of sections, the corresponding integral equation becomes: E = 0.5(I _H +I _G +0.5(I _C +I _D ))

using the same notation used in the paper by Wang et. al. (Wang, W-J., Zhu, S., Macromolecules 33 (2000), 1157). The equations used to estimate the absolute propylene content were not modified.

The molar percentage of comonomer incorporation was calculated from the molar fraction:

E (mol.%)=100*fE

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

E (mass %)=100*(fE*28.06)/((fE*28.06)+((1-fE)*42.08))

The comonomer sequence distribution at the triad level was determined using the analysis method of Kakugo et al. (Kakugo, M., Naito, Y., Mizunuma, K., Miyatake, T. Macromolecules 15 (1982) 1150). This method was chosen for its robustness, and the integration domains were slightly adjusted to increase applicability to a wider range of comonomer contents.

Xylene soluble fraction (XCS, wt. %): Xylene cold soluble fraction (XCS) content is determined at 25°C in accordance with ISO 16152; 2005.

DSC analysis, melting point (Tmelting point) and crystallization temperature (Tcr): measurements are carried out using a TA Instrument Q2000 differential scanning calorimetry (DSC) instrument on samples from 5 to 7 mg. DSC operates in accordance with ISO 11357 / part 3 / method C2 in the heating/cooling/heating cycle with a scanning speed of 10°C/min in the temperature range from -30 to +225°C.

The crystallization temperature (Tcr) and crystallization enthalpy (Hcr) are determined at the cooling stage, while the melting temperature (Tmelt) and melting enthalpy (Npl) are determined at the second heating stage.

The flexural modulus is determined in accordance with ISO 178 on 80 x 10 x 4 mm ³ injection molded test plates in accordance with EN ISO 1873-2.

The longitudinal (machine) and transverse tensile modulus was determined in accordance with ISO 527-3 at 23°C on cast films of 50 μm thickness produced on a single-layer cast film line with a melt temperature of 220°C and a chill roll temperature of 20°C , 50 µm thick, produced as follows. The test was carried out with a lateral head speed of 1 mm/min.

Transmittance, haze and clarity are determined in accordance with ASTM D1003-00 on 50 µm cast films produced as follows.

Welding initiation temperature (SIT); (welding end temperature (SIT), welding range):

This method determines the sealing temperature range (seal range) of polypropylene films, in particular blown films or cast films. The sealing temperature range is the temperature range in which films can be sealed according to the conditions given below. The lower limit (seal start temperature (SIT)) is the seal temperature at which seal strength >3 N is achieved. The upper limit (seal end temperature (SET)) is reached when the films adhere to the sealer. The sealing range is determined using a J&B Universal Sealing Machine Type 3000 on 50 µm film with the following additional parameters:

The samples were welded "A to A" at each welding plate temperature, and the weld strength (force) was determined at each stage. The temperature at which the welding force reaches 3 N was determined.

Hot Tack Pull Force: Hot Tack Pull Force was determined in accordance with ASTM F1921-12 - Method B using a J&B Hot-Tack Tester on 50 µm film produced from a single-layer cast film production line.

All film samples were prepared under standard conditioning and testing atmospheres at 23°C (±2°C) and 50% relative humidity (±10%).

The minimum time for conditioning the test sample in a standard atmosphere before testing is at least 16 hours. The minimum storage time between extrusion of the film sample and the start of testing is at least 88 hours.

The hot tack peel force measurement determines the strength of the heat seal produced on the films immediately after the seal has been performed and before it has cooled to ambient temperature. Peel force measurements for hot tack determination were carried out under the following conditions.

Film sample width: 25.4 mm.

Welding bar length: 50 mm;

Welding bar width: 5 mm;

Welding bar shape: flat

Welding pressure: 0.3 N/mm ² ;

Welding time: 0.5 s.

Cooling time: 99 s;

Peeling speed: 200 mm/s.

Initial temperature: 90°C;

Final temperature: 140°C;

Increments: 10°C.

The hot tack peel force was measured as a function of temperature over a temperature range and in temperature increments as described above. The number of test samples was at least 3 samples for each temperature. The result of this method is a hot tack test curve showing the force versus temperature curve.

The hot tack peel force (HTS) was estimated from the curve as the highest force (maximum peak value) with a “peel” tear pattern.

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 holding for 30 minutes at 121°C, they were immediately removed from the steam sterilizer and stored at room temperature until further processing.

Determination of Al and Zr (Inductively Coupled Plasma (ICP) Method) In a glove box, an aliquot of the catalyst (about 40 mg) was weighed into a glass weighing dish using an analytical balance. The sample was then exposed to air overnight while placed in a steel secondary container equipped with an air inlet. 5 ml of concentrated (65%) nitric acid was then used to rinse the contents of the boat into a microwave-safe Xpress container (20 ml). The sample was then microwave hydrolyzed using a MARS 6 laboratory microwave unit for 35 minutes at 150°C. The hydrolyzed sample was allowed to cool for at least 4 hours and then transferred to a 100 ml glass volumetric flask. standard solutions containing 1000 mg/L Y and Rh (0.4 ml) were added. Then the flask was filled with distilled water and shaken well. The solution was filtered through 0.45 μm nylon syringe filters and then analyzed using a Thermo iCAP 6300 ICP-30 OES and iTEVA software.

The device was calibrated for Al, B, Hf, Mg, Ti and Zr using a blank solution (5% HNO ₃ solution) and six standards - 0.005 mg/l, 0.01 mg/l, 0.1 mg/l, 1 mg /l, 10 mg/l and 100 mg/l Al, B, Hf, Mg, Ti and Zr in solutions of 5% HNO ₃ in distilled water. However, not every calibration point was used for every wavelength. Each calibration solution contained 4 mg/L Y and Rh standards. Al 394.401 nm was calibrated using the following calibration points: blank, 0.1 mg/L, 1 mg/L, 10 mg/L, and 100 mg/L. Al 167.079 nm was calibrated as Al 394.401 nm excluding 100 mg/L, and Zr 339.198 nm using standards - blank, 0.01 mg/L, 0.1 mg/L, 1 mg/L, 10 mg/L and 100 mg/l. For the calibration curves, a curvilinear fit and a 1/concentration weighting were used.

Immediately before analysis, the calibration was checked and refined (instrument recalibration function) using a blank solution and a standard of 10 mg/L Al, B, Hf, Mg, Ti and Zr, which contained 4 mg/L Y and Rh. Quality control sample (QC: 1 mg/l Al, Au, Be, Hg and Ce; 2 mg/l Hf and Zr, 2.5 mg/l As, B, Cd, Co, Cr, Mo, Ni, P, Sb, Sn and V; 4 mg/l Rh and Y; 5 mg/l Ca, K, Mg, Mn, Na and Ti; 10 mg/l Cu, Pb and Zn; 25 mg/l Fe and 37.5 mg /l Ca in a solution of 5% HNO ₃ in distilled water) was used to confirm the recalibration for Al, B, Hf, Mg, Ti and Zr. A quality control sample was also used at the end of the planned set of analyses.

The Zr content was monitored using the Zr 339.198 nm line {99}. The aluminum content was monitored using the 167.079 nm {502} line when the Al concentration in the test portion was less than 2 wt. % and using the line 394.401 nm {85} for Al concentrations above 2 wt. %. Y 371.030 nm {91} was used as an internal standard for Zr 339.198 nm, and Al 394.401 nm and Y 224.306 nm {450} for Al 167.079 nm.

The obtained values were recalculated back to the original catalyst sample using the initial weight of the catalyst aliquot and the dilution volume.

2. Examples

The catalyst used in the polymerization processes to produce the C ₂ C ₃ random copolymer in the example according to the invention (IE1) was prepared as follows:

Metallocene (MC1) (rac-anti-dimethylsilanediyl(2-methyl-4-phenyl-5-methoxy-6-tert-butyl-indenyl)(2-methyl-4-(4-tert-butylphenyl)indenyl)zirconium dichloride)

synthesized according to the procedure as described in WO 2013007650, E2.

The catalyst was prepared using metallocene MC1 and a catalyst system—MAO and trityl tetrakis(pentafluorophenyl)borate. The catalyst was supported on silicon dioxide.

Preparation of MAO-silica support A steel reactor equipped with a mechanical stirrer and a filter mesh was purged with nitrogen and the reactor temperature was set at 20°C. Then DM-L-303 grade silicon dioxide from AGC Si-Tech Co, pre-calcined at 600°C (7.4 kg), after which the pressure was carefully pressurized and released with nitrogen through manual valves. Toluene (32 kg) was then added. The mixture was stirred for 15 minutes. After this, 30 wt. was added. % MAO solution in toluene (17.5 kg) from Lanxess through a feed line from the top of the reactor for 70 min. The reaction mixture was then heated to 90°C and stirred at 90°C for an additional two hours. The suspension was left to settle and the mother liquor was filtered. The MAO-treated carrier was washed twice with toluene (32 kg) at 90°C, followed by precipitation and filtration. The reactor was cooled to 60°C and the solid was washed with heptane (32.2 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 (-50 kPa g (-0.5 bar g) with stirring. The MAO-treated support was collected as white powder, in which 12.6 wt.% Al was found.

Preparation of the catalyst system for examples IE1 and IE2 according to the invention 30 wt. % MAO in toluene (2.2 kg) was added to a steel reactor filled with nitrogen through a burette at 20°C. Toluene (7 kg) was then added with stirring. Metallocene MC1 (286 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. Trityl tetrakis (pentafluorophenyl) borate (336 g) was then added from a metal cylinder followed by rinsing with 1 kg of toluene. The mixture was stirred for 1 hour at room temperature. The resulting solution was added with stirring to the MAO-silica support filter cake prepared as described above for 1 hour. The filter cake was kept for 12 hours, after which it was dried in a stream of N ₂ at 60°C for 2 hours and an additional 5 hours in vacuum (-50 kPa at the pressure gauge (-0.5 bar at the pressure gauge)) with stirring . The dried catalyst was taken in the form of a pink free-flowing powder containing 13.9 wt. % Al and 0.26 wt. % Zr.

For comparative examples CE1 and CE2, a Ziegler-Natta catalyst was used.

Preparation of Ziegler-Natta catalyst for CE1 and CE2 Chemicals used:

20% solution in toluene of butyl ethyl magnesium (Mg(Bu)(Et), BEM), supplied by Chemtura;

2-ethylhexanol, supplied by Amphochem;

3-Butoxy-2-propanol-(DOWANOL™PnB), available from Dow; bis(2-ethylhexyl)citraconate, supplied by SynphaBase; TiCl ₄ , available from Millenium Chemicals;

Toluene, provided by Aspokem; Viskoplex® 1-254, supplied by Evonik; Heptane, supplied by Chevron.

Preparation of Mg alkoxy compound A solution of Mg alkoxide was prepared by adding 20 wt. to 11 kg with stirring (70 rpm). % solution of butylethylmagnesium (Mg(Bu)(Et)) in toluene, a mixture of 4.7 kg of 2-ethylhexanol and 1.2 kg of butoxypropanol in a 20 L stainless steel reactor. During addition, the contents of the reactor were maintained at a temperature below 45°C. After completion of the addition, stirring (70 rpm) of the reaction mixture was continued at 60°C for 30 minutes. After cooling to room temperature, 2.3 kg of donor bis(2-ethylhexyl)citraconate was added to the Mg-alkoxide solution, maintaining the temperature below 25°C. Mixing was continued for 15 minutes with stirring (70 rpm).

Preparation of Solid Catalyst Component 20.3 kg TiCl ₄ and 1.1 kg toluene were added to a 20 L stainless steel reactor. While stirring at 350 rpm and maintaining the temperature at 0°C for 1.5 hours, 14.5 kg of the Mg alkoxy compound prepared as described above was added. 1.7 L of Viscoplex® 1-254 and 7.5 kg of heptane were added and after 1 hour of stirring at 0°C, the temperature of the resulting emulsion was raised to 90°C for 1 hour. After 30 minutes, stirring was stopped, the catalyst drops solidified, and the resulting catalyst particles settled. After settling (1 hour), the supernatant liquid was pumped out through a siphon. The catalyst particles were then washed with 45 kg of toluene at 90°C for 20 minutes, followed by two washes with heptane (30 kg, 15 min). During the first wash with heptane, the temperature was reduced to 50°C, and during the second wash - to room temperature.

The catalyst thus obtained was used together with triethylaluminum (TEAL) as a cocatalyst and dicyclopentyldimethoxysilane (D-donor) as a donor to prepare polymers CE1 and CE2.

Polymerization to produce the C ₂ C ₃ random copolymer (RACO) according to the invention, as well as polymers CE1 and CE2, was carried out in a Borstar pilot plant with a two-reactor configuration (loop reactor - gas phase reactor (GPR 1)).

Table 1 shows the polymerization conditions for IE1 and IE2. Table 2 shows the polymerization conditions for CE1 and CE2, and CE3 is identical to that described in example 1 according to the invention (IE1) in EP 3064514 A1.

All polymer powders were mixed in a Coperion ZSK 57 co-rotating twin-screw extruder at 220°C with 0.2 wt. % release agent (synthetic silicon dioxide; CAS-no.7631-86-9); 0.1 wt. % antioxidant (Irgafos 168FF); 0.1 wt. % sterically hindered phenol (Irganox 1010FF); 0.02 wt. % Ca stearate) and 0.02 wt. % non-lubricating stearate (synthetic hydrotalcite; CAS-no. 11097-59-9).

The inventive C ₂ C ₃ random copolymers (RACO) and comparative polymers were processed into single-layer cast films of 50 μm thickness on a PM30 casting line (laboratory type extruder, manufactured by Plastik Maschinenbau GmbH., Germany). The equipment consists of an extruder, a roller cooler with an air knife and a winding machine.

A 3-zone PP screw, 30 mm in diameter, 25D in length, with a 200 mm extrusion head, 0.5 mm head slot gap, was used in combination with a remote slot head assembly with an angled inlet channel.

The extrusion parameters were as follows:

Extruder temperature profile: 220°C/240 ^° C/250 ^° C/260 ^° C/260°C (melt temperature 250°C; melt pressure 6.1 MPa (61 bar)); extruder speed: 50 rpm; chill roll temperature: 20°C; exit speed: 10.2 m/min.

Table 5 shows the optical parameters (before sterilization, d.s.), as well as the sealing characteristics (SIT and HTF), tensile modulus and R-factor for examples according to the invention. Table 6 shows the corresponding data for the comparative examples.

The films were then sterilized with steam.

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 holding them for 30 minutes at 121°C, they were immediately removed from the steam sterilizer and stored at room temperature until further processing.

Optical parameters after sterilization (ps) are given in table 7 for examples according to the invention and in table 8 for comparative examples.

From the above tables it is clear that the C ₂ C ₃ random copolymers according to the invention (RACO) are characterized by the advantageous combination of low sealing initiation temperature (SIT), high peel force when determining hot tack and good optical properties such as low turbidity and high transparency, as well as good resistance to sterilization.

Claims (63)

1. C ₂ C ₃ random copolymer (RACO) with a bimodal distribution of comonomer content, having (a) ethylene content from 2.8 to 4.9% by weight; (b) melt flow index PTR ₂ (230°C/2.16 kg), measured in accordance with ISO 1133, from 1.0 to 20.0 g/10 min; (c) melting point Tm, determined by differential scanning calorimetry (DSC) in accordance with ISO 11357, from 115 to 130 °C, and (d) content of xylene cold soluble (XCS) fraction from 0.5 wt.% to less than 15.0 wt.%. 2. C ₂ C ₃ statistical copolymer (RACO) according to claim 1, additionally having (e) the crystallization temperature Tcr, determined by DSC in accordance with ISO 11357, from 75°C to 110°C, preferably from 80°C to 105°C, and (f) flexural modulus, determined in accordance with ISO 178 on injection molded specimens, from 500 to less than 1000 MPa, preferably from 550 to 900 MPa. 3. C ₂ C ₃ random copolymer (RACO) according to claim 1 or 2, where C ₂ C ₃ random copolymer (RACO) contains from 30.0 to 70.0 wt.% polymer fraction (RACO-1), having (i) ethylene content from 1.5 to 5.5% by weight and (ii) melt flow index PTR2 (230°C/2.16 kg), measured in accordance with ISO 1133, from 4.0 to 15.0 g/10 min, and from 70.0 to 30.0 wt.% polymer fraction (RACO-2), having (i) ethylene content from 3.5 to 7.0% by weight and (ii) melt flow index PTR2 (230°C/2.16 kg), measured in accordance with ISO 1133, from 4.0 to 12.0 g/10 min, Moreover, the ethylene content in the polymer fraction (RACO-1) is lower than the ethylene content in the polymer fraction (RACO-2). 4. C ₂ C ₃ random copolymer (RACO) according to any one of paragraphs. 1-3, wherein C ₂ C ₃ random copolymer (RACO) is produced, preferably prepared in the presence of a metallocene catalyst. 5. C ₂ C ₃ random copolymer (RACO) according to any one of paragraphs. 1-4 having (a) melt flow index PTR ₂ (230°C/2.16 kg), measured in accordance with ISO 1133, from 7.0 to 15.0 g/10 min, and/or (b) ethylene content from 3.0 to 4.8% by weight, and/or (c) crystallization temperature Tcr, determined by DSC in accordance with ISO 11357, from 82°C to 100°C, and/or (d) flexural modulus, determined in accordance with ISO 178 on injection molded specimens from 600 to 900 MPa. 6. C ₂ C ₃ random copolymer (RACO) according to any one of paragraphs. 1-5, having a melting point Tm, determined by DSC in accordance with ISO 11357, from 118 to 128°C, preferably from 120 to 126°C. 7. C ₂ C ₃ random copolymer (RACO) according to any one of paragraphs. 1-6, having a xylene cold soluble fraction (XCS) content of from 2.0 to less than 14.0 wt.%, preferably from 5.0 to less than 13.0 wt.%. 8. A method for producing C ₂ C ₃ random copolymer (RACO) according to any one of paragraphs. 1-7, wherein the C ₂ C ₃ random copolymer (RACO) is produced by polymerizing propylene and ethylene in a sequential polymerization process comprising at least two reactors connected in series, in the presence of a metallocene catalyst comprising (i) a complex of formula (I): (I) Where M represents zirconium or hafnium; each X represents a sigma ligand; 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, C ₁ -C ₂₀ -hydrocarbyl, tri(C ₁ -C ₂₀ -alkyl)silyl, C ₆ -C ₂₀ -aryl, C ₇ -C ₂₀ -arylalkyl or C ₇ - C ₂₀ -alkylaryl; R ² and R ^2' each independently represent a C ₁ -C ₂₀ hydrocarbyl radical, possibly containing one or more heteroatoms from groups 14-16; R ^5' represents a C _1-20 hydrocarbyl group containing one or more heteroatoms from groups 14-16, optionally substituted with one or more halogen atoms; R ⁶ and R ^6' each independently represent hydrogen or a C _1-20 hydrocarbyl group, optionally containing one or more heteroatoms from groups 14-16; where R ^6` preferably represents a tertiary alkyl group; R ⁷ represents hydrogen or a C _1-20 hydrocarbyl group, optionally containing one or more heteroatoms from groups 14-16; R ^7' represents hydrogen; Ar and Ar' each independently represent an aryl or heteroaryl group having up to 20 carbon atoms, optionally substituted by one or more R ¹ groups; each R ¹ represents a C _1-20 hydrocarbyl group, or two R ¹ groups on adjacent carbon atoms taken together may form a fused 5- or 6-membered non-aromatic ring with an Ar group, said ring itself possibly being substituted with one or more groups ^R4 ; each R ⁴ represents a C _1-20 hydrocarbyl group; and (ii) a cocatalyst containing at least one or two Group 13 metal compounds. 9. The method for producing C ₂ C ₃ random copolymer (RACO) according to claim 8, where the cocatalyst includes at least an Al and/or boron compound. 10. A method for producing C ₂ C ₃ random copolymer (RACO) according to claim 8 or 9, where the method includes the following steps: a) polymerization in the first reactor (R1) of propylene and ethylene to obtain the polymer fraction (RACO-1) C ₂ C ₃ random copolymer (RACO), b) transferring said polymer fraction (RACO-1) and unreacted comonomers from the first reactor to the second reactor (R2), c) feeding said second reactor (R2) propylene and ethylene, d) polymerization in said second reactor (R2) and in the presence of said polymer fraction (RACO-1) of propylene and ethylene to obtain a polymer fraction (RACO-2), wherein said polymer fraction (RACO-1) and said polymer fraction (RACO-2) form a C ₂ C ₃ random copolymer (RACO), as defined in paragraphs. 1-8. 11. Method according to any one of paragraphs. 8-10, in which a cocatalyst system including a boron cocatalyst and an alumoxane cocatalyst is used as the cocatalyst (ii), and the catalyst is supported on a silica support. 12. Use of C ₂ C ₃ random copolymer (RACO) according to any one of paragraphs. 1-11 for the manufacture of products. 13. Use according to claim 12, wherein the products are sterilizable or sterilized products. 14. A sterilizable or sterilized product comprising a C ₂ C ₃ random copolymer (RACO) according to any one of claims. 1-11. 15. Sterilizable or sterilized product according to claim 14, which is a sterilizable or sterilized film. 16. A sterilizable or sterilized product comprising a C ₂ C ₃ random copolymer (RACO) according to any one of paragraphs. 1-11, where the products are films that are characterized by the following properties: (i) weld initiation temperature, SIT, defined as the lowest weld temperature at which a weld strength of >3 N is achieved, from 80°C to less than 120°C, (ii) hot tack pull force, determined according to ASTM F1921-12 Method B on 50 µm cast film, greater than 1.5 N to 6.0 N, (iii) haze, determined in accordance with ASTM D1003-00 on 50 µm cast film, from 0.05% to less than 2.00% and haze, determined in accordance with ASTM D 1003-00 on 50 µm cast film, after sterilization, steam sterilization at 121°C for 30 minutes, from 0.30% to less than 7.00%, and (iv) transparency, determined in accordance with ASTM D1003-00 on 50 µm cast films, from at least 85.0% to 100.0% and transparency, determined in accordance with ASTM D1003-00 on 50 µm cast films, after sterilization, steam sterilization at 121°C for 30 minutes, from at least 75.0% to 98.0%. 17. Sterilizable or sterilized product according to claim 16, which are films additionally having a tensile modulus determined in accordance with ISO 527-3 at 23°C on cast films with a thickness of 50 μm in the processing direction, as well as in the transverse direction , in the range from 300 to 600 MPa. 18. Sterilizable or sterilized product according to claim 16 or 17, which is a film having a resistance coefficient (R-factor) according to the formula from more than 3000 to 6000, where The tensile modulus (TE) is determined in accordance with ISO 527-3 at 23°C on cast films with a thickness of 50 µm in the processing direction, HTF hot tack peel force measured on 50 µm cast film and Turbidity before sterilization is determined according to ASTM D1003-00 on 50 µm thick cast film before sterilization. 19. The use of a sterilizable or sterilized product, which is a film, according to any of paragraphs. 16-18 as a sealing layer in a multilayer film. 20. A flexible packaging system selected from bags or bags for foodstuffs and medicines, including a sterilizable or sterilized product, which is a film, according to any one of paragraphs. 16-18.