JP7213989B2 - Polymers for high speed production of biaxially oriented films, films and articles made therefrom - Google Patents

Description

The present invention relates to polypropylene for preparing films, particularly biaxially oriented polypropylene (BOPP) films. Due to the claimed structural properties of polypropylene, BOPP films can be manufactured without plate-out formation and without the use of slip additives (e.g., metal stearates) known to facilitate the film manufacturing process. The speed of the process for preparing the can be increased to 450 m/min or more. The invention also relates to a BOPP film, at least one layer of which comprises polypropylene. The films according to the invention are suitable for producing packaging, including food packaging, adhesive tapes, labels and the like.

Polypropylene film is a popular material for producing high quality flexible packaging, as it can have different properties depending on its composition and method of manufacture. In particular, biaxially oriented polypropylene (BOPP) films are used in the manufacture of packaging for food and non-food products, individual or multi-unit packaging. Here, these packages can be clear, metallized, matt, or (depending on the color of the filler) colored. In addition, BOPP films are used for the production of labels, adhesive tapes and the like.

As a rule, the main component of BOPP films is isotactic polypropylene with an isotacticity of 87-89% (isotacticity is measured by isotactic pentads [mmmm] by C ¹³ NMR analysis). determined by the fraction.). The presence of a certain number of defects in the structure of isotactic macromolecules contributes to the polymer's higher ability to orient. Polypropylene's higher orientation capability, in turn, allows for increased process speeds and increased film yields.

It is also known that increasing the xylene soluble fraction in the polymer leads to improved alignment capabilities of the polymer. At the same time, however, the prior art leads to the release of a large number of low molecular weight fractions during the processing of such polymers, their subsequent combustion, and their deposition on equipment to form plate-outs. known to be The latter in particular leads to frequent equipment shutdowns for cleaning, which leads to increased equipment downtime.

From EP 2143116 a heat resistant film is known. At least one layer of the film has a melt flow rate of 0.5 to 15 g/10 min and a cold xylene soluble fraction value of less than 3.5 wt%; It contains a polypropylene with a determined degree of crystallinity and a xylene and heptane insoluble fraction content of more than 94% by weight. The film further comprises at least a second layer containing a heterophasic statistical copolymer (impact copolymer), the heterophasic statistical copolymer having a melt flow rate of 0.5 to 15.0 g/10 min and It has a melting point of 120-170°C. The film is characterized by high tear strength, impact strength and puncture resistance due to its low content of cold xylene soluble (XCS) fraction. A disadvantage of this solution proposed in EP 2 143 116 is the slow processing speed of polypropylene due to the low content of cold xylene soluble fractions.

From EP 0925912 high metal adhesion films and metallized films are known. The core layer is made of isotactic polypropylene with an isotactic pentad [mmmm] fraction of 88% or more, preferably 90% or more, and Mw/Mn in the range of 2-6. At the same time, however, other properties of the isotactic polypropylene (content of fractions with specific molecular weights and fractions soluble in xylene and heptane) are not disclosed. The process speed is also not specified.

Also known from EP 0 831 994 is a method for producing BOPP films. The core layer of this film contains polypropylene with a degree of atacticity of at least 10% or an isotactic polymer with a degree of atacticity of less than 5%, atactic polypropylene, syndiotactic polypropylene, ethylene-propylene copolymer , propylene terpolymer, polybutene, or a mixture with a linear low density polyethylene polymer. By using polypropylene or polymer compositions with a degree of atacticity of 10% or more, BOPP films with high tear resistance can be obtained. There are no other demands on the properties of isotactic polypropylene. Therefore, the content of fractions with specific molecular weights and fractions with specific solubilities in xylene and heptane are not considered important indicators for determining the suitability of polypropylene for use in film processing processes. not done.

Thus, structural properties of polypropylene for use in the manufacture of BOPP films that allow processing at speeds of at least 450 m/min while maintaining the degree of film strength properties required according to regulatory documents. The complete combination of is not yet known.

European Patent No. 2143116 EP 0925912 EP 0831994

It is an object of the present invention to determine a combination of structural properties of polypropylene that make it possible to increase the efficiency of the polypropylene stretching (biaxial orientation) process to obtain BOPP films.

The technical result of the present invention is a BOPP film by using in the film composition a polypropylene whose structural properties allow the film to be processed at a speed of at least 450 m/min. to improve the productivity of the process of obtaining

Technical results of the present invention also include that no plate-out is formed on the die during the film manufacturing process.

A further technical result is the possibility to obtain a wide range of films such as clear, matt, filled, general purpose, etc. and to apply layered coatings such as metallized layers, printing.

The subject of the present invention is a polypropylene having the following properties:
- the amount of cold xylene soluble fraction (XCS) in the polymer is in the range of 4.0 to 6.0% by weight, wherein the amount of cold xylene soluble fraction having a molecular weight of 50,000 g/mole or more The proportion is at least 60% by weight, while the proportion of cold xylene soluble fractions with molecular weights in the range from 1,500 to 50,000 g/mol does not exceed 40% by weight; and - heptane solubility in the polymer. the amount of fraction (HS) is in the range of 2.5-3.5% by weight, wherein the proportion of heptane-soluble fractions with a molecular weight of 50,000 g/mol or more is at least 60% by weight On the other hand, it was solved by introducing into the film a polypropylene having a proportion of heptane soluble fractions with a molecular weight in the range of 1,500 to 50,000 g/mol not exceeding 40% by weight, the technology significant results have been achieved.

The inventors have found that specific contents of xylene soluble and heptane soluble fractions, characterized by specific molecular weight values, increase the process speed for producing biaxially oriented films, improving the orientation of polypropylene. I found that it is possible by doing. While not wishing to be bound by any particular theory, the inventors believe that to reduce the adverse effects of increased plate-out formation on the forming die and to preserve polypropylene's orientation ability, polypropylene should be Given that it must contain a certain amount of XS and HS fractions with a content of low molecular weight (1,500-50,000 g/mol) and high molecular weight (greater than 50,000 g/mol) components there is

Figure 2 shows a BOPP film prepared from polypropylene according to the invention; 3 shows a BOPP film prepared in Example 3. FIG. 4 shows a BOPP film prepared in Example 4. FIG. 4 shows a BOPP film prepared in Example 5. FIG.

The following is a detailed description of various aspects and implementations of the invention.

The polypropylene to be used for film preparation has the following properties:
- The content of the cold xylene soluble fraction (hereinafter referred to as "XCS") is in the range of 2.5 to 4.0% by weight, preferably in the range of 4.0 to 6.0% by weight. and - the heptane soluble fraction (hereinafter referred to as "HS") content is in the range of 2.5 to 3.5% by weight.

A unique property of the claimed polypropylene to be used in the production of BOPP films is that the molecular weight of the XCS fraction is primarily in the range of 1,500 to 50,000 g/mol, whereas the molecular weight of the XCS fraction is 50 ,000 g/mole, does not exceed 40% by weight, preferably does not exceed 30% by weight, more preferably does not exceed 20% by weight.

Another essential characteristic of the claimed polypropylene used for the production of BOPP films is that the proportion of the HS fraction with a molecular weight above 50,000 g/mol is at least 60% by weight, preferably at least 65% by weight. % by weight, most preferably at least 70% by weight, and the proportion of HS fractions with molecular weights between 1,500 and 50,000 g/mol does not exceed 40% by weight, preferably 25% by weight. not exceed, more preferably not exceed 15% by mass.

Increasing the proportion of low molecular weight components (having a molecular weight not exceeding 50,000 g/mol) in the heptane-soluble and xylene-soluble fractions reduces the mechano-physical properties of the film and reduces the resulting in increased formation of plate-outs to

Preferably, the polypropylene has a molecular weight distribution of 4-7, more preferably 5-7.

Preferably, the isotactic pentad [mmmm] content of the polypropylene is 87-89%.

The present invention provides a polymer for preparing BOPP films at high process speeds (at least 450 m/min), which is supported Ziegler _- Natta titanium of the general _formula MgCl2/ _{TiCl4 /} D1/D2/ - can be obtained using a magnesium catalyst. _In the formula, titanium tetrahalide is supported on magnesium halide, D1 is the internal electron donor, D2 is the external electron donor and triethylaluminum ₍ TEA) is the promoter.

As D1 any compound known from the prior art as a donor for Ziegler _- Natta catalysts is used. This compound contains at least one of the following functional groups: an alcohol, amino, amido, or ester group. Specific examples of internal donors include methanol, ethanol, isopropanol, and butanol; diethylamine, diisopropylamine, and triethylamine; formamide and acetamide, C ₁ -C ₂₀ benzoic acid alkyl esters, C ₁ -C ₈ of aliphatic monocarboxylic acids. Including, but not limited to, alkyl esters, 1,8-naphthyl diesters; malonic esters, succinic esters, and glutaric esters. However, in the present invention, it is not recommended to use fourth-generation Ziegler-Natta catalysts (including phthalate compounds as donors) and internal electron donors represented by fluorene compounds.

As D ₂ an organosilicon compound of the following formula: R _n Si(OR) _4-n can be used. In the formula, R is a hydrocarbon radical, OR is an alkoxy group, R is a hydrocarbon group, and n is an integer of 0<n<4. Examples of organosilicon compounds of this formula that can be used in the present invention include: diisopropyldimethoxysilane, tert-butylmethyldimethoxysilane, tert-butylmethyldiethoxysilane, tert-amylmethyldi ethoxysilane, dicyclohexyldimethoxysilane, cyclohexylmethyldimethoxysilane, cyclohexylmethyldiethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, tert-butyltriethoxysilane, phenyltriethoxysilane, cyclohexyltrimethoxysilane, cyclopentyltrimethoxysilane, 2-methylcyclopentyltrimethoxysilane, cyclopentyltriethoxysilane, n-propyltrimethoxysilane, dicyclopentyldimethoxysilane, dicyclopentyldiethoxysilane, tricyclopentylmethoxysilane, dicyclopentylmethylmethoxysilane, dicyclopentylethylmethoxysilane, and cyclopentyl dimethylethoxysilane.

It is known to those skilled in the art that the properties of polypropylene (proportions of xylene-soluble and heptane-soluble fractions and their molecular weight distribution) depend on both the nature and amount of the external electron donor used in the catalyst system. . Preferably, the external electron donor is added at a molar ratio of cocatalyst (Co) to external electron donor (ED) in the range of 2-180 [Co/ED ratio].

More specific examples of the catalysts described and methods for their preparation are disclosed in EP 2 221 320, EP 2 638 080, EP 2 951 215.

The polypropylene of the present invention can be obtained by gas-phase or suspension polymerization of propylene in the presence of the catalysts mentioned above. In any of the polymerization methods used, the components of the catalyst system (catalyst, cocatalyst, and optionally external electron donor) can be contacted with each other before they are added to the polymerization reactor. Alkyl-Al compounds such as triethylaluminum, diethylaluminum chloride, triisobutylaluminum, tri-n-butylaluminum, tri-n-hexylaminealuminum, tri-n-octylaluminum, etc. can be used as cocatalysts. .

Polymerization using Ziegler-Natta catalysts is generally carried out at temperatures in the range 50-80° C., preferably 65-75° C., and in the range 0.1-5.0 MPa, preferably 0.5-3.5 MPa. is carried out at operating pressures in the range of

Preferably, in order to maintain the physico-mechanical properties of the films produced, the melt flow index (MFI _{230°C/2.16 kg} ) of the polymer used, determined according to ASTM D 1238, is at least 3 g /10 min.

In particular, polypropylene can be prepared, for example, according to the methods described in US Pat. No. 8,178,633, EP 2,726,517, and the like.

These methods of manufacturing the exemplary polypropylene make it possible to achieve the above properties, but they are not the only ones. Polypropylene with the specified properties can be obtained by other methods known from the prior art.

Preferably, the polypropylene comprises a stabilizer comprising at least a mixture of antioxidants and acid absorbers. Any antioxidant known from the prior art can be used as antioxidant, preferably a mixture of a phosphite antioxidant and a phenolic antioxidant is used. As acid absorbers it is possible to use any acid absorbers known from the prior art, with the exception of absorbers from the class of metal stearates. Additionally, other known additives may be further used to enable the polypropylene to retain its properties during processing and operation. The amount of stabilizer added to polypropylene is 1-3 kg per ton of polypropylene, preferably 1.2-2.5 kg per ton of polypropylene, more preferably 1.2-1.5 kg per ton of polypropylene.

The polypropylene according to the invention is substantially free of calcium stearate. Calcium stearate converts to stearic acid upon interaction with acid. Stearic acid readily migrates to the surface of the film, making the production of metallized films impossible. The expression "substantially free" means a content of less than 0.010% by weight, preferably less than 0.005% by weight, most preferably less than 0.001% by weight.

The specified polypropylene can be used as a major component or as an additional component of any film layer of any formulation known from the prior art. The exact structure of the film (number and sequence of layers) and layer content will depend on the requirements for the film and the products made from it.

In addition to the polypropylene of the present invention, films may contain other polyolefins as well as functional polymers. As polyolefins, α-olefin copolymers and terpolymers are used, specifically copolymers of propylene and ethylene, copolymers of propylene and butene, terpolymers of propylene, ethylene and butene, and the like. The following compounds are used as functional polymers: copolymers of ethylene with vinyl alcohol, polyvinylidene chloride; copolymers of vinylidene chloride, polyesters, polyamides (to impart anti-gas and/or anti-odor properties to films); ethylene. and α-olefin interpolymers (for adhesiveless paper-film lamination); maleic anhydride homopolypropylene (adhesive layer in coextruded films), and the like.

In a first embodiment of the present invention, the film is intended for the manufacture of wrapping paper as a base for adhesive tapes or the like, each layer comprising polypropylene having the properties described above and antistatic and/or anti-caking substances and/or Or it is a multilayer polypropylene film consisting of an antioxidant. Antiblocking agents include silicon dioxide (SiO ₂ ), polymethyl methacrylate (PMMA) and the like, and antioxidants are phenolic antioxidants.

In a second embodiment of the invention, the film is intended for an adhesive-free film-paper lamination and comprises at least: a core layer containing polypropylene having the properties described above, and Functionalized layer comprising: ethylene-butene copolymer, ethylene-octene copolymer, ethylene-butene-octene terpolymer, grafted maleic anhydride modified ethylene-butene copolymer, grafted maleic anhydride modified ethylene - octene copolymers, ethylene-butene-octene terpolymers modified with grafted maleic anhydride, or mixtures thereof, or formed from any of the listed copolymers and/or terpolymers, modified copolymers and/or terpolymers. and blends with hydrogenated petroleum resins.

In a third embodiment of the invention, the film is a barrier film and comprises at least the following layers: one layer of a propylene polymer having the properties described above, and a copolymer of polyamide, ethylene and vinyl alcohol, represented by the like. layer of gas barrier material applied. A layer of modified polyolefin (e.g., a layer of maleic anhydride-modified propylene polymer) can optionally be used to improve adhesion between the layer of propylene polymer and the layer of gas barrier material that meet the properties described above. can.

Other embodiments of the invention will be apparent to those skilled in the art and are not disclosed in detail in the description of the invention. For example, additives can be included in the formulation in effective amounts, ie, amounts that provide desired functional properties or improve the parameters and/or functionality of the final film. In particular, examples of additives include, but are not limited to: additives that provide anti-caking, antistatic, and slipping benefits, as well as antioxidants and neutralizers, technical additives, Nucleating agents, additives that reduce the effects of UV radiation, and UV absorbers, dyes, fillers, thickeners, modifiers based on hydrocarbon resins, and the like.

The total thickness of the film varies widely depending on its intended use. In a preferred embodiment, the film has a total thickness of 2-100 μm, preferably 5-50 μm, more preferably 10-30 μm.
The films of the present invention are obtained by coextrusion of polypropylene with other polymers and subsequent stretching. The orientation value of the film in the machine direction is 4.5-5.5 and up to 10 in the transverse direction.

A film prepared according to the present invention after stretching can be processed according to the following procedure.
1. Embossing on the surface of the film.
2. The surface of the film is activated/modified (eg by plasma treatment, corona treatment, flame treatment) to make it suitable for printing.
3. The prepared film is laminated onto a woven or nonwoven material, especially paper, foil or other film.
4. Deposition of metal layers (e.g. deposition of aluminum layers by vacuum techniques based on condensation of metal vapors).
5. An adhesive layer is applied on one or both sides of the film to obtain an adhesive film.

Optionally, the treated film is used to produce final products such as packaging, metallized packaging, labels, bags, adhesive tapes and other articles using BOPP films according to the invention. Specific examples include making labels as specified in EP2197669, WO2017/077184, making bags as disclosed in particular in US9108391, e.g. 205381, the manufacture of metallized films as described in EP 0925912;

[Test method]:
1. Melt Flow Index (MFI) was measured according to ASTM D1238.
2. The mass fraction of soluble fraction in the boiling heptane/isotactic fraction was determined according to National State Standard 26996-86.
3. The mass fraction of the p-xylene soluble fraction was determined according to ISO16152.
4. Polypropylene samples and statistical copolymer samples of propylene and ethylene were measured for molecular weight distribution (MWD) by Gel Permeation Chromatography (GPC) on an Agilent PL-GPC 220 system according to ISO 16014-4-2012: High temperature method. went by The dissolution temperature was 150° C. and the solvent was 1,2,4-trichlorobenzene.
5. Measurement of molecular weight characteristics of xylene soluble (XCS) and heptane soluble (HS) substances from samples is based on low temperature GPC method with Agilent 1200 liquid chromatograph (manufactured by Agilent) in accordance with ISO16014-4-2012: low temperature method. I did. The measured dissolution temperature was 40° C. and the solvent was tetrahydrofuran.
6. The microstructure, isotacticity, and pentad ratio of polypropylene samples were determined by high-resolution nuclear magnetic resonance spectroscopy ( ¹³ C NMR) of carbon nuclei on a Bruker Avance III 400 MHz NMR spectrometer. For research purposes, 250 μg of sample was dissolved in 2.5 ml of trichlorobenzene while heating to 140°C. The number of scans for ¹³ С nuclei is 16,000. The measurement temperature was 140°C.

The invention is illustrated in more detail by the following examples. The examples are provided to illustrate the invention and are not intended to limit its scope.

[Example 1]
A propylene polymer with an MFI of 3.0 g/10 min (230° C. and 2.16 kg) was obtained by gas phase technology at a temperature of 65-75° C. and an operating pressure of 2.2 MPa. As catalyst, a catalyst prepared in the same way as Example 6 of EP 0361493 was used, except that diisobutyldimethoxysilane was used as the external electron donor.

The BOPP film is a five-layer film, each layer of which comprises the polypropylene described above, and an antioxidant such as the hindered phenolic antioxidant pentaerythritol tetraoxy(3-(3,5-di-tert-butyl- 4-hydroxyphenyl)propionate) (Irganox 1010) and tris(2,4-di-tert-butylphenyl)phosphite (Irgafos 168) as a phosphorus-containing antioxidant], and hydrotalcite as an acid absorber. in an amount of 1.35 kg stabilizer per ton of polypropylene. Films were prepared by continuous extrusion of polypropylene, stepwise orientation, heat curing, and cooling of the film slabs. The melted material plasticized in each extruder (5 extruders corresponding to the number of layers) is combined in the die (head), the confluent is allowed to flow from the slot die to the cooling drum (shaft) in the form of a slab, and then The slab was cooled by passing it through a water bath. The film slab was then reheated to 100-115° C. on a heated cylinder and stretched on rollers to 6 times its original length in the machine direction. The machine direction stretched film was placed in an oven, heated again with air to a maximum of 170-180° C., and stretched in the cross direction to 10 times its original width. The total film thickness was 20 µm, the outer layer being 0.9 µm, the intermediate layer being 2.5 µm, and the core layer being 13.2 µm. The properties of the polypropylene used and the processing speed of the film are shown in Table 1.

[Example 2]
A BOPP film was prepared similar to Example 1, except that the polypropylene had the properties shown in Example 2 in Table 1, and the film was five layers, each of which consisted of polypropylene. The process speed of the film is shown in Table 1.

[Example 3 (Comparison)]
Except that the BOPP film was prepared using a Ziegler-Natta catalyst with dibutyl phthalate as the internal electron donor and the polypropylene had the properties shown in Table 1, Comparative Example 3. and prepared in the same manner as in Example 1. The process speed of the film is shown in Table 1.

[Example 4 (Comparison)]
The BOPP film used polypropylene prepared using a Ziegler-Natta catalyst with 9,9-bismethoxymethylfluorene as the internal electron donor, and the polypropylene exhibited the properties shown in Table 1, Comparative Example 4. Prepared as in Example 1, except with The process speed of the film is shown in Table 1.

[Example 5 (Comparison)]
A BOPP film was prepared using a Ziegler® system containing cocatalyst and external electron donor with a molar ratio of cocatalyst (Co) to external electron donor (ED) [Co/ED ratio] of 40 (to achieve low XCS). Prepared similarly to Example 1, except that a polypropylene prepared using a Natta catalyst was used and the polypropylene had the properties shown in Table 1, Comparative Example 5. The process speed of the film is shown in Table 1.

[Example 6 (Comparison)]
Except that the BOPP film was prepared using a Ziegler-Natta catalyst with isobutyl phthalate as the internal electron donor and the polypropylene had the properties shown in Table 1, Comparative Example 6. and prepared in the same manner as in Example 1. The process speed of the film is shown in Table 1.

From Table 1 it can be seen that the process speed of polypropylene is very high (450 m/min) when the cold xylene soluble fraction content is between 4 and 6% by weight. However, physical This results in a significant reduction in mechanical properties and rapid deposition of low molecular weight fractions on the die surface followed by combustion, leading to frequent equipment shutdowns for cleaning maintenance. be done. At the same time, if the requirements for the content of the low molecular weight fraction are met (Example 6), the time for plate-out formation (deposition of amorphous carbon) can be extended (however, in the case of this Example 6, the process speed is limited to 380 m/min).

Therefore, in order to achieve high process speeds of 450 m/min or more, ensure high physico-mechanical properties of the film, and reduce the extent of plate-out formation, the following combination of properties should be observed:
- the amount of cold xylene soluble fraction (XCS) in the polymer is in the range of 4.0-6.0% by weight;
- the amount of heptane soluble fraction (HS) in the polymer is in the range of 2.5-3.5% by weight;
- the proportion of cold xylene soluble fraction (XCS) with a molecular weight of 50,000 g/mol or more in the polymer is at least 60% by weight;
- the proportion of the cold xylene soluble fraction (XCS) with a molecular weight of 1,500 to 50,000 g/mol in the polymer is not more than 40% by weight;
- the proportion of heptane soluble fraction (HS) with a molecular weight of 50,000 g/mol or more in the polymer is at least 60% by weight;
- the proportion of heptane soluble fraction (HS) with a molecular weight between 1,500 and 50,000 g/mol in the polymer is not more than 40% by weight;

Claims (29)

A polypropylene for making a biaxially oriented film, comprising:
The polypropylene has the following properties:
- the amount of cold xylene soluble fraction (XCS) in the polymer is in the range of 4.0 to 6.0% by weight, wherein the amount of cold xylene soluble fraction having a molecular weight of 50,000 g/mole or more The proportion is at least 60% by weight, while the proportion of cold xylene soluble fractions with molecular weights in the range from 1,500 to 50,000 g/mol does not exceed 40% by weight; and - heptane solubility in the polymer. the amount of fraction (HS) is in the range of 2.5-3.5% by weight, wherein the proportion of heptane-soluble fractions with a molecular weight of 50,000 g/mol or more is at least 60% by weight while the proportion of the heptane-soluble fraction having a molecular weight in the range from 1,500 to 50,000 g/mol does not exceed 40% by weight
(Here, the molecular weights of the xylene soluble fraction (XCS) and the heptane soluble fraction (HS) are values measured by the low temperature GPC method in accordance with ISO16014-4-2012: low temperature method.)
polypropylene. The polypropylene according to claim 1, having a molecular weight distribution of 4-7. 3. Polypropylene according to claim 2, having a molecular weight distribution of 5-7. The polypropylene of claim 1, wherein the polypropylene has an isotactic pentad (mmmm) fraction of 87-89%. 2. Polypropylene according to claim 1, wherein the polypropylene contains stabilizers including at least one antioxidant and at least one acid absorber. 6. Polypropylene according to claim 5, wherein the polypropylene contains at least one phenolic antioxidant and at least one phosphite antioxidant as stabilizers. 7. Polypropylene according to claim 5 or 6, wherein the polypropylene contains hydrotalcite as acid absorber. wherein the polypropylene contains 1-3 kg of stabilizer per ton of polypropylene, or 1.2-2.5 kg of stabilizer per ton of polypropylene, or 1.2-1.5 kg of stabilizer per ton of polypropylene; The polypropylene according to claim 5. The polypropylene according to claim 1, wherein the polypropylene contains 0% by mass or more and less than 0.010% by mass of calcium stearate. Polypropylene according to claim 1, wherein the amount of cold xylene soluble fraction (XCS) is in the range of 4.5-5.5% by weight. 2. Polypropylene according to claim 1, wherein the proportion of cold xylene soluble fraction (XCS) having a molecular weight of 50,000 g/mol or more is at least 65 % by weight, or at least 70% by weight. Polypropylene according to claim 1, wherein the proportion of the heptane soluble fraction (HS) with a molecular weight between 1,500 and 50,000 g/mol does not exceed 25 % by weight, or does not exceed 15% by weight. 2. Polypropylene according to claim 1, wherein the proportion of heptane soluble fraction (HS) with a molecular weight of 50,000 g/mol or more is at least 65 % by weight, or at least 70% by weight. A film comprising at least one layer comprising polypropylene,
The polypropylene has the following properties:
- the amount of cold xylene soluble fraction (XCS) in the polymer is in the range of 4.0 to 6.0% by weight, wherein the amount of cold xylene soluble fraction having a molecular weight of 50,000 g/mole or more the proportion is at least 60% by weight, while the proportion of cold xylene soluble fractions with molecular weights in the range from 1,500 to 50,000 g/mol does not exceed 40% by weight;
- the amount of heptane soluble fraction (HS) in the polymer is in the range of 2.5-3.5% by weight, wherein the heptane soluble fraction having a molecular weight of 50,000 g/mol or more The proportion is at least 60% by weight, while the proportion of heptane-soluble fractions with molecular weights in the range from 1,500 to 50,000 g/mol does not exceed 40% by weight.
(Here, the molecular weights of the xylene soluble fraction (XCS) and the heptane soluble fraction (HS) are values measured by the low temperature GPC method in accordance with ISO16014-4-2012: low temperature method.)
a film. 15. The film of claim 14, wherein the polypropylene has a molecular weight distribution of 4-7. 16. The film of claim 15, wherein the polypropylene has a molecular weight distribution of 5-7. 15. The film of claim 14, wherein the polypropylene has an isotactic pentad (mmmm) fraction of 87-89%. 15. The film of claim 14, wherein the polypropylene contains stabilizers including at least one antioxidant and at least one acid absorber. 19. The film of claim 18, wherein said polypropylene contains at least one phenolic antioxidant and at least one phosphite antioxidant as said stabilizer. 20. A film according to claim 18 or 19, wherein the polypropylene contains hydrotalcite as acid absorber. 18. The polypropylene according to claim 17, wherein the polypropylene contains 1-3 kg per ton of polypropylene, or 1.2-2.5 kg per ton of polypropylene, or 1.2-1.5 kg per ton of polypropylene. the film. 15. The film of claim 14, wherein the polypropylene comprises 0% by weight or more and less than 0.010% by weight of calcium stearate. 15. The film of claim 14, wherein the amount of cold xylene soluble fraction in the polypropylene is in the range of 4.5-5.5% by weight. 15. The film of claim 14, wherein the proportion of cold xylene soluble fractions having a molecular weight of 50,000 g/mole or more is at least 65 % by weight, or at least 70% by weight. 15. A film according to claim 14, wherein the proportion of heptane soluble fractions with a molecular weight between 1,500 and 50,000 g/mol does not exceed 25% by weight, or does not exceed 15% by weight. 15. The film of Claim 14, wherein the film is produced by coextrusion. 15. The film of Claim 14, wherein the film is a biaxially oriented film. Use of the film according to any one of claims 14-27 for the manufacture of articles. An article comprising the film of any one of claims 14-27.

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