JP7213988B2 - 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, the speed of the process for preparing BOPP films has been increased to 450 m/m without the use of slip additives (e.g. metal stearates) known to facilitate the film manufacturing process. can be increased to minutes 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.

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 the production of BOPP film by using polypropylene in the film composition, whose structural properties allow the film to be processed at speeds of at least 450 m/min. It lies in improving the productivity of the process to obtain.

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) is in the range of 2.5-4.0% by weight, wherein the molecular weight of said cold xylene soluble fraction is mainly 1,500-50,000 g/ while within the range of moles, the proportion of fractions with a molecular weight above 50,000 g/mol does not exceed 30% by weight; in the range of 5 to 3.5% by weight, wherein the proportion of polymers having a molecular weight of 400,000 to 3,000,000 g/mol is not more than 10% by weight and from 1,500 to The proportion of components with a molecular weight of 50,000 g/mol was solved by introducing polypropylene into the film with a content of at least 60% by weight, the technical result being 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 to obtain biaxially oriented films by improving the orientation of polypropylene. I found it possible. Without wishing to be bound by any particular theory, the inventors believe that a high content (60% by weight or more) of the heptane soluble fraction of low molecular weight (1,500-0,000 g/mol) , is believed to improve orientation during the processing process of polymer macromolecules, which in turn increases process speeds up to 450 m/min or more.

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 3.0 to 3.8% 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 30% by weight, preferably does not exceed 15% by weight, more preferably does not exceed 5% by weight.

Another essential characteristic of the claimed polypropylene used for the production of BOPP films is that the proportion of HS fractions with molecular weights between 400,000 and 3000,000 g/mol does not exceed 10% by weight. , preferably not more than 7 wt. 70% by weight, most preferably at least 75% by weight.

When the amount of the heptane soluble fraction is less than 2.5% by weight, or at a total content of the HS fraction within the specified range of 2.5-3.5% by weight, the composition of the HS fraction is The proportion of low molecular weight (molecular weight 1,500-50,000 g/mol) components decreases and/or the proportion of high molecular weight (molecular weight 400,000-3,000,000 g/mol) components changes to increase In some cases, this results in poor processability of the polymer.

An amount of heptane soluble fraction above 3.5% by weight leads to a decrease in the physico-mechanical properties of the film as well as an increase in the formation of carbon on the spinneret during the processing process.

The processability of the film and its properties are also affected by varying the amount and composition of the XCS fraction.

Therefore, if the amount of XCS fraction is less than 2.5% by weight, the processability of the film is reduced, which is due to the reduced ability of the polymer used to orient macromolecules, regardless of its molecular weight characteristics. caused by.

When using a polymer with an XCS fraction of more than 4.0% by weight in the preparation of a film, its physico-mechanical properties decrease, and during the polymer-to-film process, the An increased formation of carbon deposits is observed.

Preferably, the polypropylene has a molecular weight distribution of 5-7, more preferably 6-7.

Preferably, the isotactic [mmmm] fraction content of the polymer is between 87 and 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. In particular, D ₁ may be selected from the following compounds:

Group of Alcohols: Preferred alcohols are compounds of formula R ¹ OH, where the R ¹ group represents a C ₁ -C ₂₀ hydrocarbon group. In a more preferred embodiment, R ¹ is a C ₁ -C ₂₀ alkyl group. Specific examples are methanol, ethanol, isopropanol, and butanol.

Group of Amines: Preferred amines are compounds of formula NR ² ₃ , wherein the R ² groups are, independently of each other, hydrogen or C ₁ -C ₂₀ hydrocarbon groups, provided that they are not all hydrogen at the same time. . In a more preferred embodiment, R ² is a C ₁ -C ₂₀ alkyl group. Specific examples are diethylamine, diisopropylamine, and triethylamine.

Group of Amides: Preferred amides are of the formula R ³ CONR ⁴ ₂ , where R ³ and R ⁴ are independently of each other hydrogen or C ₁ -C ₂₀ hydrocarbon groups. Specific examples are formamide and acetamide.

Group of esters: Preferred esters are aromatic carboxylic acid monoesters, such as benzoic acid esters, especially C ₁ -C ₂₀ alkyl benzoates, aliphatic carboxylic acid monoesters, such as C ₁ -C ₈ alkyl esters, etc., and 1,8-naphthyl diesters.

Another group are C ₁ -C ₂₀ alkyl esters of aromatic dicarboxylic acids, such as phthalates, and C ₁ -C ₂₀ alkyl esters of aliphatic dicarboxylic acids, such as malonates, succinates, glutarates. etc. In addition, diesters of diols can also be used.

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.

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. Copolymers and terpolymers of α-olefins, specifically copolymers of propylene and ethylene, copolymers of propylene and butene, terpolymers of propylene, ethylene and butene, etc., are used as polyolefins. The following compounds are used as functional polymers: copolymers of ethylene and vinyl alcohol, polyvinylidene chloride, copolymers of vinylidene chloride, polyesters, polyamides (to impart anti-gas and/or anti-odor properties to films), ethylene and Interpolymers of α-olefins (for adhesive-free 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, represented by polyamides, copolymers of ethylene and vinyl alcohol, etc. layer of gas barrier material. A layer of modified polyolefin, such as a layer of maleic anhydride-modified propylene polymer, can optionally be used to improve the adhesion between the layer of propylene polymer and the layer of gas barrier material that meet the properties described above. .

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 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. The molecular weight characteristics of xylene soluble (XCS) substances and heptane soluble (HS) substances from samples were measured by low temperature GPC method with Agilent 1200 liquid chromatograph (manufactured by Agilent) in accordance with ISO16014-4-2012: low temperature method. rice field. The measured dissolution temperature was 40° C. and the solvent was tetrahydrofuran.
6. 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. The catalyst used was prepared in the same manner as in Example 1 of US Pat. No. 9,284,392, 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 process speed of the film are shown in Table 1.

[Example 2]
A BOPP film was prepared as in Example 1, except that the polypropylene had the properties shown in Table 1. The process speed of the film is shown in Table 1.

[Example 3]
A BOPP film was prepared as in Example 1, except using a polypropylene having the properties shown in Table 1. The process speed of the film is shown in Table 1.

[Example 4 (Comparison)]
BOPP film using a polypropylene obtained using a Ziegler-Natta catalyst containing an internal electron donor such as dibutyl phthalate (described in EP 0 193 281) and the properties of the polypropylene shown in Table 1 Prepared as in Example 1, except having The process speed of the film is shown in Table 1.

[Example 5 (Comparison)]
BOPP film using polypropylene obtained using a Ziegler-Natta catalyst containing an internal electron donor such as 9,9-bis-methoxymethyl-fluorene (described in US Pat. No. 8,003,559), and Prepared as in Example 1, except the polypropylene had the properties shown in Table 1. The process speed of the film is shown in Table 1.

[Example 6 (Comparison)]
BOPP films were obtained using Ziegler-Natta catalysts containing multicomponent internal electron donors such as (3,3-bis(methoxymethyl)-2,6-dimethylheptane and diethyl 2,3-diisopropylsuccinate). A BOPP film was prepared similar to Example 1, except that a polypropylene (described in US Patent Application Publication No. 2016/0102159) was used and the polypropylene had the properties shown in Table 1. The process speed of the film is shown in Table 1.

[Example 7 (Comparison)]
BOPP films are polypropylene obtained using Ziegler-Natta catalysts containing multi-component internal electron donors such as (9,9-bis-methoxymethyl-fluorene and diethyl 2,3-diisopropylsuccinate) (US patent No. 8003559) and the polypropylene had the properties shown in Table 1. The process speed of the film is shown in Table 1.

From the table it can be seen that the process speed of polypropylene depends entirely on its structural properties. The amount of the xylene-soluble polypropylene fraction and the heptane-soluble polypropylene fraction containing large amounts of macromolecules with high molecular weights (>50,000 g/mol for XCS, 400,000-3,000,000 g/mol for HS) When increased (compared to the polypropylene according to the invention), the process speed cannot be increased to 450 m/min (as in Comparative Examples 4, 6 and 7). When using a polypropylene that has the same amount of XCS fraction as the polypropylene of the present invention, but the amount of heptane soluble fraction does not fall within the range disclosed in the present invention (Example 5), the amount of A process speed of 450 m/min is not achieved due to the excess high molecular weight component. Considering the results obtained in Examples 1, 2, 3, where the heptane and xylene soluble fraction values with the specified molecular weights are within the ranges disclosed in the present invention, achieving high speeds in the processing process is necessary. It can be said that it is a result that as a whole conforms to the characteristics to be considered.

Therefore, in order to achieve process speeds of 450 m/min or more, the following characteristics are required:
- the amount of cold xylene soluble fraction (XCS) in the polymer is in the range of 2.5-4.0% by weight, where the molecular weight of the polymer is mainly 1,500-50,000 g/ and - the amount of heptane soluble fraction (HS) in the polymer is 2.5 to 3.5% by weight, wherein the proportion of polymers having a molecular weight of 400,000 to 3,000,000 g/mol is not more than 10% by weight, and 1,500 to 50% by weight. Overall it must be observed that the proportion of components with a molecular weight of .000 g/mol is at least 60% by weight.

Claims (28)

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 2.5-4.0% by weight, wherein the molecular weight of the macromolecules of said cold xylene soluble fraction is a proportion of at least 70% by weight of components with a molecular weight in the range from 1,500 to 50,000 g/mol, while a proportion of components with a molecular weight above 50,000 g/mol not exceeding 30% by weight; and - the amount of heptane soluble fraction (HS) in the polymer is in the range of 2.5-3.5% by weight, wherein it has a molecular weight of 400,000-3,000,000 g/mol The proportion of polymers is not more than 10% by weight and the proportion of components having a molecular weight of 1,500 to 50,000 g/mol is at least 60% 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 5-7. 3. Polypropylene according to claim 2, having a molecular weight distribution of 6-7. The polypropylene according to claim 1, wherein the polypropylene has an isotactic pentad [mmmm] fraction of 87-89%. Polypropylene according to claim 1, wherein the polypropylene contains stabilizers comprising at least one antioxidant and at least one acid absorber, wherein the acid absorber does not belong to the class of metal stearates. . 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 3.0-3.8% by weight. 2. Polypropylene according to claim 1, wherein the proportion of cold xylene soluble fraction (XCS) with a molecular weight above 50,000 g/mol does not exceed 15% by weight, or does not exceed 5% by weight. 2. Polypropylene according to claim 1, wherein the proportion of heptane soluble fraction (HS) with a molecular weight between 1,500 and 50,000 g/mol is at least 70% by weight, or at least 75% 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 2.5 to 4.0% by weight, wherein the molecular weight of the polymer of said cold xylene soluble fraction is 1,500 a proportion of at least 70% by weight of components with a molecular weight in the range of ˜50,000 g/mol, while a proportion of components with a molecular weight above 50,000 g/mol not exceeding 30% by weight;
- the amount of heptane soluble fraction (HS) in the polymer is in the range of 2.5-3.5% by weight, wherein high The proportion of molecules should be no more than 10 mass and the proportion of components with molecular weights between 1,500 and 50,000 g/mol should be at least 60 mass.
(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. 14. The film of claim 13, wherein the polypropylene has a molecular weight distribution of 5-7. 15. The film of claim 14, wherein the polypropylene has a molecular weight distribution of 6-7. 14. The film of claim 13, wherein the polypropylene has an isotactic pentad [mmmm] fraction of 87-89%. 14. Film according to claim 13, wherein the polypropylene contains stabilizers comprising at least one antioxidant and at least one acid absorber, wherein the acid absorber does not belong to the class of metal stearates. . 18. The film of claim 17, wherein said polypropylene contains at least one phenolic antioxidant and at least one phosphite antioxidant as said stabilizer. 18. The film of Claim 17, wherein the polypropylene contains hydrotalcite as an 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. 14. The film of claim 13, wherein the polypropylene comprises 0% or more and less than 0.010% by weight of calcium stearate. 14. The film of claim 13, wherein the amount of cold xylene soluble fraction (XCS) in the polypropylene is within the range of 3.0-3.8 wt%. 14. A film according to claim 13, wherein the proportion of cold xylene soluble fraction (XCS) having a molecular weight above 50,000 g/mol in the polypropylene does not exceed 15% or does not exceed 5% by weight. 14. The film according to claim 13, wherein the proportion of heptane soluble fraction (HS) having a molecular weight of 1,500 to 50,000 g/mol in the polypropylene is at least 70% by weight, or at least 75% by weight. 14. The film of Claim 13, wherein the film is produced by coextrusion. 14. The film of Claim 13, wherein the film is a biaxially oriented film. Use of the film according to any one of claims 13-26 for the manufacture of articles. An article comprising the film of any one of claims 13-26.