DE9307735U1 - Opaque, matt polypropylene multilayer film - Google Patents

Description

HOECHST AKTIENGESELLSCHAFT KALLE-ALBERT plant

93/K034G - 1 - 17.5.1993

WL-DC.Fa-bl

Opaque, matt polypropylene multilayer film

The innovation relates to an opaque polypropylene multilayer film which comprises at least one base layer containing polypropylene or a polypropylene mixture and fillers, and at least one intermediate layer and at least one cover layer applied to this intermediate layer, the cover layer essentially

a propylene homopolymer or 10 a copolymer of

Ethylene and propylene or ethylene and butylene or propylene and butylene or

ethylene and another &sgr;-olefin having 5 to 10 carbon atoms or

Propylene and another &sgr;-olefin having 5 to 10 carbon atoms or
a terpolymer of

Ethylene and propylene and butylene or
ethylene and propylene and another &sgr;-olefin with 5 to 10

Carbon atoms or

a mixture of two or more of the above-mentioned homo-, co- and terpolymers or

a blend of two or more of the above-mentioned homo-, co- and terpolymers, optionally mixed with one or more of the

called homo-, co- and terpolymers,

and the intermediate layer contains a mixture or blend of two components I and II.

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Component I of the mixture or blend is a propylene homopolymer or a copolymer of σ-olefins having 2 to 10 carbon atoms or a terpolymer of σ-olefins having 2 to 10 carbon atoms or a mixture of two or more of the homo-, co- and terpolymers mentioned or a blend of two or more of the homo-, co- and terpolymers mentioned.

Component II of the mixture or blend is a high density polyethylene (HDPE) or a blend of HDPE and one or more other polymers selected from the group of propylene homopolymer, copolymer of σ-olefins having 2 to 10 carbon atoms, terpolymer of σ-olefins having 2 to 10 carbon atoms, and a blend of co- and terpolymers of σ-olefins having 2 to 10 carbon atoms.

The new film is characterized by a characteristic matt look.

The innovation also relates to a process for producing the multilayer film and its use.

The German patent application P 41 35 096.0 discloses polyolefin multilayer films made of a polypropylene base layer and a cover layer made of an HDPE blend. This HDPE blend consists of HDPE and co- and/or terpolymers made of σ-olefins and optionally polypropylene. The cover layer of the multilayer film has a minimal gloss and a maximum haze, which gives the film a characteristic matt appearance.

DE-A-16 94 694 discloses multilayer films consisting of biaxially oriented polypropylene films and containing at least one heat-sealable layer made of an ethylene-propylene copolymer. These films have a

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good heat sealability, they are clear and not scratch-resistant to the desired degree and also show insufficient processing properties on high-speed packaging machines.

EP-A-0 008 904 discloses a biaxially oriented three-layer polyolefin film that can be sealed on both sides, in which the base layer is made of propylene polymers and the two sealing layers are made of sealable olefin polymers. However, this polyolefin film is transparent and, in particular, only slightly scratch-resistant and cannot be printed on. In addition, it leaves something to be desired in various ways with regard to its sliding properties on high-speed packaging machines.

Another biaxially oriented polyolefin film with three layers that can be sealed on both sides is known from US-A-4 419 411. In these films, polysiloxane and silicon dioxide are incorporated as an additive combination in both sealing layers. The base layer consists essentially of polypropylene and contains a small amount of monocarboxylic acid amide, which partially migrates from the base layer into the two sealing layers. The polyolefin multilayer film described is said to have a particularly low coefficient of friction. This

20 The main disadvantage of film is that it cannot be printed on.

US-A-4 578 316 discloses a biaxially oriented polyolefin multilayer film, the base layer of which consists of a polypropylene homopolymer and the cover layer of a blend of polypropylene and MDPE and/or HDPE. This polyolefin film has a low coefficient of friction in conjunction with a surface that is easily wettable; however, this film also has excellent optical transparency.

WO 89/10839 describes polyolefin multilayer films whose base layer consists of a propylene polymer and whose cover layers consist of either

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made of HDPE or an ethylene-propylene copolymer or a polypropylene where the film is stretched under specific temperature conditions. In particular, it has a low coefficient of friction and good wettability, but at the same time also a high gloss and low haze.

EP-AO 367 613 discloses a multilayer film made of a vacuole-containing polypropylene base layer and a cover layer which can be written on and contains a first polymer with a melt flow index of <1 g/10 min and a second polymer which is incompatible with said first polymer. As an example of the first polymer, an HDPE with a density of 0.92 to 0.97 g/cm ³ is described. The incompatible polymer is a polypropylene or copolymers of propylene or terpolymers of propylene. The film described has an opaque appearance, ie it is essentially impermeable to light.

It is described that the film takes on a matt appearance when it is printed on. It is preferable to incorporate a filler into the cover layer to improve the ability to write on it, while at the same time the SiGy-containing cover layer has a high mattness, which gives the film a paper-like appearance. The described film has a density of 0.69 g/cm ^3. The matt, SiCy-containing surface proves to be in need of improvement when printing. The color has a gray haze and does not have a uniform appearance. This is attributed to inhomogeneities, which do not appear so strong in the film itself due to its opacity, but come out when printing. The printed films are spotty and

25 are not accepted by the processor.

Many state-of-the-art films have the disadvantage of chalking, i.e. after a few days a layer of dust forms on the films, which consists of particles that do not come from the environment but from the film itself, in particular from its cover layers.

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All state-of-the-art films need improvement in terms of their economic disadvantages and their variation options. The visual appearance of conventional films can be varied by suitable measures, for example the whiteness of a film can be increased by incorporating TiO ₂ into the cover layer. However, such modifications generally not only lead to the desired change, but also inevitably affect other film properties, for example TiO ₂ in the cover layer changes not only the whiteness but also the roughness and thus the running properties of the film. These side effects, some of which are very undesirable, mean that processors have to re-optimize the processing conditions for each type of film, ie readjust individual packaging machines or change printing ink compositions, etc. Such necessary measures have previously been viewed as self-evident and unavoidable.

The aim of this innovation was therefore to provide a multilayer film that is characterized by a matt appearance of the film. The gloss of the film should be optimized with regard to this desired matt characteristic. At the same time, a homogeneous film appearance without spotty or streaky defects is important. In addition, good surface properties, in particular a high and long-term surface tension of the top layer, are required to ensure that it can be printed on well. At the same time, a uniform appearance of the print is required.

Depending on its intended use, the film may also need to have good sealing properties, in particular a large sealing area and good heat sealability. In addition, good running properties and low friction are required for the intended use on high-speed packaging machines.

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According to the innovation, this task is solved by a multilayer film of the type mentioned above, whereby
Component I essentially

a propylene homopolymer or a copolymer of

Ethylene and propylene or ethylene and butylene or propylene and butylene or

ethylene and another &sgr;-olefin having 5 to 10 carbon atoms 10 or

Propylene and another &sgr;-olefin having 5 to 10 carbon atoms or
a terpolymer of

Ethylene and propylene and butylene or
15 ethylene and propylene and another &sgr;-olefin with 5 to 10

Carbon atoms or

a mixture of two or more of the above-mentioned homo-, co- and terpolymers or

a blend of two or more of the above-mentioned homo-, co- and ter-20polymers, optionally mixed with one or more of the

called homo-, co- and terpolymers, and
Component II is essentially a HDPE or

contains a blend of two blend components A and B, where

the blend component A essentially

is a HDPE and

the blend component B is essentially a propylene homopolymer or a copolymer of

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Ethylene and propylene or ethylene and butylene or propylene and butylene or

Ethylene and another &sgr;-olefin having 5 to 10 carbon atoms or

Propylene and another &sgr;-olefin having 5 to 10 carbon atoms or
a terpolymer of

Ethylene and propylene and butylene or
Ethylene and propylene and another &sgr;-olefin with

5 to 10 carbon atoms or

a mixture of two or more of the above-mentioned homo-, co- and terpolymers or
a blend of two or more of the above-mentioned homo-, co- and terpolymers

is
and the film is matt.

Mixtures in the sense of the present innovation are understood to mean mechanical mixtures which are produced from the individual components. In general, the individual components are poured together as small-sized pressed bodies, e.g. lens-, spherical- or rod-shaped granules, and mixed mechanically using a suitable vibrating device.
25

A blend in the sense of the present innovation is an alloy-like combination of individual components, which can no longer be broken down into its original components. A blend has properties like a homogeneous substance and can be characterized accordingly by suitable parameters.

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The base layer of the multilayer film according to the innovation essentially contains a propylene polymer or a polypropylene mixture and fillers.

The propylene polymer of the base layer contains predominantly (at least 90%) propylene and has a melting point of 140 ^° C or higher, preferably 150 to 170 ^° C. Isotactic homopolypropylene with an n-heptane-soluble portion of 6% by weight and less, based on the isotactic homopolypropylene, copolymers of ethylene and propylene with an ethylene content of 10% by weight or less, copolymers of propylene with C ₄ -C ₈ -σ-olefins with a σ-olefin content of 10% by weight or less are preferred propylene polymers for the base layer, with isotactic homopolypropylene being particularly preferred. The percentages by weight given refer to the respective copolymer. The propylene polymer of the core layer generally has a melt flow index of 0.5 g/10 min to 8 g/10 min, preferably 2 g/10 min to 5 g/10 min, at 230 ⁰ C and a force of 21.6 N (DIN 53 735).

Furthermore, a mixture of the above-mentioned propylene homopolymers and/or copolymers and/or other polyolefins compatible with the propylene polymers, in particular with 2 to 6 carbon atoms, is suitable, the mixture containing at least 50% by weight, in particular at least 75% by weight, of propylene polymer. Other suitable polyolefins in the polymer mixture are compatible polyethylenes, in particular HDPE, LDPE and LLDPE, the proportion of these polyolefins not exceeding 15% by weight, based on the polymer mixture. "Compatible" in the sense of the present innovation means that the compatible polymer is not present in the film as a separate phase.

If necessary, the propylene polymer used in the base layer can be partially degraded by adding organic peroxides. A measure of the degree of degradation of the polymer is the so-called degradation factor A, which

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indicates the relative change in the melt flow index according to DIN 53 735 of the polypropylene, relative to the starting polymer.

MFL

&sfgr; A = ²

^ü MFI ₁

MFI ₁ = Melt flow index of the propylene polymer before the addition of

organic peroxide

MFI ₂ = Melt flow index of peroxidically degraded propylene polymer

In general, the degradation factor A of the propylene polymer used is in the range of 3 to 15, preferably 6 to 10.

Diacyl peroxides are particularly preferred as organic peroxides, where an alkyl radical is understood to mean the usual saturated straight-chain or branched lower alkyl radicals with up to six carbon atoms. In particular, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane or di-t-butyl peroxide are preferred.

The polypropylene base layer generally contains fillers in an amount of 1 to 30% by weight, which make the film opaque. "Opaque film" in the sense of the present innovation means an opaque film whose light transmission (ASTM-D 1003-77) is at most 30%, preferably at most 50%.

The term "fillers" in the sense of the present innovation includes vacuole-initiating solid particles, hereinafter referred to as "solid particles", and pigments. Solid particles are incompatible with the polymer matrix and lead to the formation of vacuole-like cavities when the films are stretched, whereby the size, type and number of the vacuoles depend on the size of the solid particles and the stretching conditions such as stretch ratio and stretching temperature.

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The vacuoles give the films a characteristic pearly, opaque appearance, which is caused by light scattering at the "vacuole/polymer matrix" interfaces. The light scattering on the solid particles themselves generally contributes relatively little to the opacity of the film. As a rule , solid particles have a minimum size of 1 pm in order to lead to an effective, i.e. opaque, size and quantity of vacuoles. In general, the average particle diameter of the solid particles is 1 to 6 μνη, preferably 1.5 to 5 /μm. The chemical character of the solid particles plays a subordinate role.

Pigments are also incompatible with the polymer matrix and include fillers that hardly lead to the formation of vacuoles during stretching. The coloring effect of the pigments is caused by the particles themselves. The term "pigment" is generally linked to a particle size of 0.01 to a maximum of 1 μm and includes both so-called "white pigments" that color the films white and "colored pigments" that give the film a colorful or black color. In general, the average particle diameter of the pigments is in the range of 0.01 to 1 μm, preferably 0.01 to 0.5 μm.

Thus, the division of fillers into the two groups "solid particles" and "pigments" is a classification according to their functionality, which depends on the particle size, among other things. Solid particles make films opaque by forming vacuoles. Pigments color the film and thereby make it opaque. Both types of particles are summarized under the general term "fillers".

Common fillers in the base layer are inorganic and/or organic materials that are incompatible with polypropylene, such as aluminum oxide, aluminum sulfate, barium sulfate, calcium carbonate, magnesium carbonate, silicates such as aluminum silicate (kaolin clay) and magnesium silicate (talc), silicon dioxide and titanium dioxide, of which calcium carbonate, silicon dioxide and titanium dioxide are preferred.

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Organic fillers that can be used are the polymers that are usually used and are incompatible with the polymer of the base layer, in particular those such as HDPE, polyester, polystyrene, polyamides, halogenated organic polymers, with polyesters such as polybutylene terephthalate being preferred. "Incompatible materials or incompatible polymers" in the sense of the present innovation means that the material or polymer is present in the film as a separate particle or as a separate phase.

The amount of filler in the base layer is generally in the range of 1 to 30 wt.%, whereby the individual embodiments can contain only solid particles or only pigments or a combination of solid particles and pigments in the base layer depending on the intended use of the film or current fashion trends.

Films which are only provided with pigment (pigmented films) generally contain this in an amount of 2 to 25% by weight, in particular 3 to 20% by weight, preferably 5 to 15% by weight, based in each case on the base layer. White pigments, in particular TiO ₂ and BaSO _4, are preferred as pigments. TiO ₂ preferably has an average particle diameter of 0.01 to 0.7 /ym, in particular

20 special 0.1 to 0.5 /ym.

Films which are only equipped with vacuole-initiating solid particles generally contain these in an amount of 1 to 25% by weight. For conventional packaging films, a solid particle content of 2 to 5% by weight is preferred. For special applications, e.g. films for labels, highly filled films with 9 to 14% by weight of solid particles are also preferred. Preferred vacuole-initiating particles are CaCO ₃ , SiO ₂ , polyamides and polybutylene terephthalates. CaCO ₃ , in particular CaCO ₃ with an average particle size of 1.5 to 5 μm, is particularly advantageous.

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Films which are provided with vacuole-initiating solid particles and with pigment contain solid particles in an amount of 1 to 10 wt. %, preferably 1 to 5 wt. %, and pigment in an amount of 1 to 7 wt. %, preferably 1 to 5 wt. %. For such film types, a combination of CaCO ₃ as solid particles and TiO ₂ as pigment is preferred. This film type is also referred to as opaque white film.

The density of the films containing fillers can vary within wide limits and depends on the type and amount of fillers. The density is generally in the range of 0.4 to 1.1 g/cm ³ .

Pigmented films have a density in the order of 0.9 g/cm ³ or more, since the pigments produce almost no density-reducing vacuoles, but can themselves have a higher density than polypropylene. Preferably, the density of this type of film is in the range of 0.9 to 1.1 g/cm ³ .

Films which only contain solid particles have a reduced density of less than 0.9 g/cm ³ compared to polypropylene due to the vacuoles. For packaging films with a conventional solid particle content of 2 to 5 wt.%, the density is in the range of 0.7 to 0.85 g/cm ³ . For highly filled films with a solid particle content of 9 to 14 wt.%, the density is in the range of 0.4 to 0.7 g/cm ³ .

Films containing pigments and solid particles, especially white opaque films, have a density in the range of 0.6 to 0.85 g/cm ³ , depending on the ratio of pigment content to solid particle content.

Preferred embodiments of the pigmented films contain TiO ₂ as a white pigment. TiO ₂ is also preferred for white-opaque film types. The titanium dioxide particles preferably consist of at least 95% by weight of rutile and

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are preferably used with a coating of inorganic oxides, as is usually used as a coating for TiO ₂ white pigment in paper or paints to improve lightfastness. Particularly suitable inorganic oxides include the oxides of aluminum, silicon, zinc or magnesium or mixtures of two or more of these compounds. They are precipitated from water-soluble compounds, e.g. alkali metal, in particular sodium aluminate, aluminum hydroxide, aluminum sulfate, aluminum nitrate, sodium silicate or silicic acid, in the aqueous suspension. TiO ₂ particles with a coating are described, for example, in EP-A-0 078 633 and EP-A-0 044 515.

If necessary, the coating also contains organic compounds with polar and non-polar groups. Preferred organic compounds are alkanols and fatty acids with 8 to 30 C atoms in the alkyl group, in particular fatty acids and primary n-alkanols with 12 to 24 C atoms, as well as polydiorganosiloxanes and/or polyorganohydrogensiloxanes such as polydimethylsiloxane and polymethylhydrogensiloxane.

The coating on the TiO ₂ particles usually consists of 1 to 12 g, in particular 2 to 6 g, of inorganic oxides, optionally additionally containing 0.5 to 3 g, in particular 0.7 to 1.5 g, of organic compounds, in each case based on 100 g of TiO ₂ particles. It has proven particularly advantageous if the TiO ₂ particles are coated with Al ₂ O ₃ or with Al ₂ O ₃ and polydimethylsiloxane.

Furthermore, the base layer can optionally contain a low molecular weight resin, the proportion of which is 1 to 30% by weight, preferably 2 to 10% by weight. The softening point of the resin is between 130 and 180 ⁰ C (measured according to DIN 1995-U4, corresponds to ASTM E-28), preferably between 140 and 160 ⁰ C. Among the numerous low molecular weight resins, hydrocarbon resins are preferred, namely in the form of petroleum resins.

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Styrene resins, cyclopentadiene resins and terpene resins (these resins are described in Ullmann's Encyclopedia of Technical Chemistry, 4th edition, volume 12, pages 525 to 555). Suitable petroleum resins are described in numerous publications, such as EP-A-0 180 087, to which express reference is made here.

The multilayer film according to the invention comprises at least one intermediate layer, which contains a mixture or a blend of two components I and II, described in more detail below, and optionally added fillers and/or additives.

Component I of the intermediate layer mixture or blend essentially contains

a propylene homopolymer or 15 a copolymer of

Ethylene and propylene or ethylene and butylene or propylene and butylene or

ethylene and another &sgr;-olefin having 5 to 10 carbon atoms or

Propylene and another &sgr;-olefin having 5 to 10 carbon atoms or
a terpolymer of

Ethylene and propylene and butylene or
ethylene and propylene and another &sgr;-olefin with 5 to 10

Carbon atoms or

a mixture of two or more of the above-mentioned homo-, co- and terpolymers or

a blend of two or more of the above-mentioned homo-, co- and terpolymers, optionally mixed with one or more of the

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called homo-, co- and terpolymers.

Particularly preferably, component I consists essentially of a propylene homopolymer or of a copolymer of

Ethylene and propylene or ethylene and butylene-1 or propylene and butylene-1 or a terpolymer of
Ethylene and propylene and butylene-1 or

a mixture of two or more of the particularly preferred homo-, co- and terpolymers mentioned or of

a blend of two or more of the particularly preferred homo-, co- and terpolymers mentioned, optionally mixed with one or more of the homo-, co- and terpolymers mentioned,

in particular propylene homopolymer or statistical ethylene-propylene copolymers with

an ethylene content of 2 to 10 wt.%, preferably 5 to 8 wt.%, or
20 statistical propylene-butylene-1-copolymers with

a butylene content of 4 to 25 wt.%, preferably 10 to 20 wt.%,

each based on the total weight of the copolymer, or
statistical ethylene-propylene-butylene-1 terpolymers with

25 an ethylene content of 1 to 10 wt.%, preferably 2 to

6 wt.%, and

a butylene-1 content of 3 to 20 wt.%, preferably 8 to 10 wt.%,

each based on the total weight of the terpolymer, or 30 a blend of an ethylene-propylene-butylene-1 terpolymer and a

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Propylene-butylene-1 copolymers

with an ethylene content of 0.1 to 7 wt.% and a propylene content of 50 to 90 wt.% and a butylene-1 content of 10 to 40 wt.%,

each based on the total weight of the polymer blend,

are preferred.

The propylene homopolymer used as or in component I contains predominantly (at least 90%) propylene and has a melting point of 140 ^° C or higher, preferably 150 to 170 ^° C, with isotactic homopolypropylene with an n-heptane-soluble content of 6% by weight and less, based on the isotactic homopolypropylene, being preferred. The homopolymer of component I or the homopolymer contained therein generally has a melt flow index of 0.5 g/10 min to 15 g/10 min, preferably 1.5 g/10 min to 6 g/10 min, at 230 ^° C and a force of 21.6 N (DIN 53 735).

Component II of the interlayer mixture or blend essentially contains a HDPE or a blend which essentially comprises HDPE as blend component A and a blend component B.

For the purposes of this innovation, HDPE refers to high-pressure polyethylene which has the following properties:

1. The melt flow index MFI, measured according to DIN 53 735 or ISO 1133 at 50 N/190 ⁰ C, is in the range of greater than 1 to 50 g/10 min, preferably 5 to 45 g/10 min, in particular 5 to 25 g/10 min.

2. The viscosity number, measured according to DIN 53 728, Part 4, or ISO 1191, is in the range of 100 to 450 cm ³ /g, preferably 120 to 280 cm ³ /g.

3. The crystallinity is 35 to 80%, preferably 50 to 80%.

4. The density, measured at 23 ⁰ C according to DIN 53 479, method A, or ISO

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1183, is in the range of 0.93 to 0.97 g/cm ³ , preferably 0.95 to 0.96 g/cm ³ .

5. The melting point, measured by DSC (maximum of the melting curve, heating rate 20 °C/min), is between 120 and 150 ⁰ C, preferably between 125 and 135 ⁰ C.

The HDPE as component II as well as HDPE as blend component A is selected from the polyethylenes described above, so that component II can basically be the same HDPE as blend component A, but does not have to be identical.

The blend component B consists essentially of a propylene homopolymer or of a copolymer of 15 ethylene and propylene or

Ethylene and butylene or propylene and butylene or

ethylene and another &sgr;-olefin having 5 to 10 carbon atoms or

Propylene and another &sgr;-olefin with 5 to 10 carbon atoms

men or from
a terpolymer of

Ethylene and propylene and butylene or

ethylene and propylene and another &sgr;-olefin having 5 to 10 carbon atoms or

a mixture of two or more of the above-mentioned homo-, co- and terpolymers or of

a blend of two or more of the above-mentioned homo-, co- and terpolymers.
30

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Particularly preferably, the blend component B consists essentially of
a propylene homopolymer or
a copolymer of

Ethylene and propylene or
5 Ethylene and butylene-1 or

Propylene and butylene-1 or a terpolymer of

Ethylene and propylene and butylene-1 or

a mixture of two or more of the particularly preferred homo-, co- and terpolymers mentioned or of

a blend of two or more of the particularly preferred homo-, co- and terpolymers mentioned,
in particular propylene homopolymer or

statistical ethylene-propylene copolymers with
an ethylene content of 2 to 10 wt.%, preferably 5 to

8 wt.%, or
statistical propylene-butylene-1 copolymers with

a butylene content of 4 to 25 wt.%, preferably 10 to 20 wt.%,

each based on the total weight of the copolymer, or

statistical ethylene-propylene-butylene-1 terpolymers with

an ethylene content of 1 to 10 wt.%, preferably 2 to 6 wt.%, and

a butylene-1 content of 3 to 20 wt.%, preferably 8 to 10 wt.%,

each based on the total weight of the terpolymer, or a blend of an ethylene-propylene-butylene-1 terpolymer and a propylene-butylene-1 copolymer

with an ethylene content of 0.1 to 7 wt.% 30 and a propylene content of 50 to 90 wt.%

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and a butylene-1 content of 10 to 40 wt.%,
each based on the total weight of the polymer blend,
are preferred.

The propylene homopolymer used as or in the blend component B contains predominantly (at least 90%) propylene and has a melting point of 140 ^° C or higher, preferably 150 to 170 ^° C, with isotactic homopolypropylene with an n-heptane-soluble content of 6% by weight and less, based on the isotactic homopolypropylene, being preferred. The homopolymer of the blend component B or the homopolymer contained therein generally has a melt flow index of 0.5 g/10 min to 15 g/10 min, preferably 1.5 g/10 min to 6 g/10 min, at 230 ^° C and a force of 21.6 N (DIN 53 735).

The ratio (weight ratio) of the two blend components A and B is between A:B = 20:80 and A:B = 80:20, preferably between A:B = 40:60 and A:B = 60:40, and is particularly preferably A:B = 45:55.

The blend of components A and B has a melt flow index (DIN 53 735 at 230 ⁰ C and 21.6 N load) of 1.5 g/10 min to 12 g/10 min, preferably 2.5 g/10 min to 6 g/10 min, the melt flow index of the blend preferably being higher than that of the propylene polymer of the base layer.

The melting range of the blend is between 100 and 160 ⁰ C, preferably between 120 and 150 ⁰ C.

The ratio (weight ratio) of the two components I and II of the cover layer mixture or the blend can vary within wide limits and depends on the intended use of the multilayer film. Preferably the ratio of components I and II is in a range of l:ll =

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10:90 to l:ll = 90:10, preferably between l:ll = 30:70 to l:li = 70:30, especially at l:ll = 50:50.

The above-described intermediate layer of the multilayer film according to the invention can, in a further embodiment, additionally contain fillers, i.e. solid particles and/or pigments, which are incompatible with the intermediate layer mixture or the blend.

The addition of these fillers in the intermediate layer does not generally lead to the formation of vacuole-like cavities. This means that the intermediate layer containing fillers is essentially vacuole-free. For homopolymer-containing intermediate layers with fillers, the proportion of homopolymer must be kept correspondingly low, especially if solid particles with an average particle diameter of > 1 /vm are included. In this case, the homopolymer proportion should not exceed 25% by weight and is preferably in the range of 5 to 20% by weight, in each case based on the intermediate layer. For filler-containing intermediate layers with a homopolymer proportion of more than 25% by weight, based on the intermediate layer, fillers with a correspondingly small average particle diameter must be selected, i.e. these intermediate layers preferably contain essentially only pigments.

The fillers for the intermediate layer according to the innovation are basically the types of fillers described above for the base layer, i.e. both the solid particles with an average particle diameter of > 1 /vm, which, however, essentially do not produce vacuoles in the intermediate layer, and/or the pigments whose average particle diameter is generally 0.001 /vm to 1 /vm. As described above for the base layer, basically only solid particles or only pigments or solid particles and pigments in combination can be added to the intermediate layer.

30 will be.

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Common fillers for the intermediate layer are inorganic and/or organic materials that are incompatible with polypropylene, such as aluminum oxide, aluminum sulfate, barium sulfate, calcium carbonate, magnesium carbonate, silicates such as aluminum silicate (kaolin clay) and magnesium silicate (talc), silicon dioxide and titanium dioxide, of which calcium carbonate, silicon dioxide and titanium dioxide are preferred. Organic fillers that can be used are the polymers that are commonly used and incompatible with the polymer of the intermediate layer, in particular those such as LDPE, LLDPE, HDPE, polyesters, polystyrenes, polyamides and halogenated organic polymers, with polyesters such as polybutylene terephthalates being preferred. "Incompatible materials or incompatible polymers" in the sense of the present innovation means that the material or polymer is present in the film as a separate particle or as a separate phase.

For preferred embodiments containing TiO ₂ , the above described for the base layer is used.

The amount of filler in the intermediate layer is up to 30% by weight and is generally in a range from 1 to 25% by weight, preferably in the range from 3 to 15% by weight, very particularly preferably in the range from 4 to 12% by weight, in each case based on the intermediate layer.

Films which are only provided with pigment in the intermediate layer generally contain this in an amount of 2 to 25% by weight, in particular 3 to 20% by weight, preferably 5 to 15% by weight, based in each case on the intermediate layer. White pigments, in particular TiO ₂ and BaSO ₄ , are preferred as pigments. TiO ₂ preferably has an average particle diameter of 0.01 to 0.7 /μm, in particular 0.1 to 0.5 μνη.

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Films which are only provided with solid particles in the intermediate layer generally contain these in an amount of 1 to 25% by weight, preferably 1 to 20% by weight, based in each case on the intermediate layer. Preferred solid particles are CaCO ₃ , SiO ₂ , polyamides and polybutylene terephthalates. CaCO ₃ , in particular CaCO ₃ with an average particle size of 1 to 5 μm, is particularly advantageous.

Films which are provided with solid particles and with pigment in the intermediate layer contain solid particles in an amount of 1 to 20 wt.%, preferably 1 to 15 wt.%, very particularly preferably 1 to 12 wt.%, and pigment in an amount of 1 to 20 wt.%, preferably 1 to 15 wt.%, very particularly preferably 1 to 12 wt.%. For such types of films, a combination of CaCO ₃ as solid particles and TiO ₂ as pigment is preferred.

Furthermore, the intermediate layer can optionally contain a low molecular weight resin. Basically, the same resins are used as described for the base layer, whereby the amounts used also correspond to those used in the base layer.

According to the innovation, the opaque, matt multilayer film has a cover layer, which is applied to the intermediate layer described above.

The top layer essentially contains

a propylene homopolymer or 25 a copolymer of

Ethylene and propylene or ethylene and butylene or propylene and butylene or

ethylene and another &sgr;-olefin having 5 to 10 carbon atoms or

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Propylene and another &sgr;-olefin having 5 to 10 carbon atoms or
a terpolymer of

Ethylene and propylene and butylene or
5 ethylene and propylene and another &sgr;-olefin with 5 to 10

Carbon atoms or

a mixture of two or more of the above-mentioned homo-, co- and terpolymers or

a blend of two or more of the above-mentioned homo-, co- and ter-10polymers, optionally mixed with one or more of the

called homo-, co- and terpolymers.

Particularly preferably, the cover layer essentially contains a propylene homopolymer or a copolymer of

Ethylene and propylene or ethylene and butylene-1 or propylene and butylene-1 or a terpolymer of ethylene and propylene and butylene-1 or

a mixture of two or more of the particularly preferred homo-, co- and terpolymers mentioned or

a blend of two or more of the particularly preferred homo-, co- and terpolymers mentioned, optionally mixed with one or more of the homo-, co- and terpolymers mentioned,

in particular propylene homopolymer or

statistical ethylene-propylene copolymers with

an ethylene content of 2 to 10 wt.%, preferably 5 to 8 wt.%, or
30 statistical propylene-butylene-1-copolymers with

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a butylene content of 4 to 25 wt.%, preferably 10 to 20 wt.%,

each based on the total weight of the copolymer, or
statistical ethylene-propylene-butylene-1 terpolymers with

an ethylene content of 1 to 10 wt.%, preferably 2 to

6 wt.%, and

a butylene-1 content of 3 to 20 wt.%, preferably 8 to 10 wt.%,

each based on the total weight of the terpolymer, or a blend of an ethylene-propylene-butylene-1 terpolymer and a

Propylene-butylene-1 copolymers

with an ethylene content of 0.1 to 7 wt.% and a propylene content of 50 to 90 wt.% and a butylene-1 content of 10 to 40 wt.%,

each based on the total weight of the polymer blend,

are preferred.

The propylene homopolymer used as or in the cover layer contains predominantly (at least 90%) propylene and has a melting point of 140 ^° C or higher, preferably 150 to 170 ^° C, with isotactic homopolypropylene with an n-heptane-soluble content of 6% by weight and less, based on the isotactic homopolypropylene, being preferred. The homopolymer of the cover layer or the homopolymer contained therein generally has a melt flow index of 0.5 g/10 min to 15 g/10 min, preferably 1.5 g/10 min to 6 g/10 min, at 230 ^° C and a force of 21.6 N (DIN 53 735).

The film according to the innovation has at least three layers and always comprises the core layer K and at least one intermediate layer Z and at least one cover layer D according to a structure KZD. The choice of

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The number of layers depends primarily on the intended use, with four- and five-layer embodiments being particularly preferred, corresponding to a DZKZD structure or an asymmetrical DKZD or ZKZD structure with an "intermediate layer" as the outer layer.
5

The total thickness of the film can vary within wide limits and depends on the intended use.

The preferred embodiments of the film according to the invention have total thicknesses of 10 to 120 μm, with 20 to 100 μm, in particular 30 to 100 μm, being preferred.

The thickness of the intermediate layer(s) is in each case independently of one another 2 to 12 μνη, with intermediate layer thicknesses of 3 to 8 μνη, in particular 3 to 6 μνη, being preferred. The values stated refer in each case to one intermediate layer.

The thickness of the cover layer(s) is greater than 0.4 μm and is preferably in the range from 0.8 to 4 μm, in particular 1 to 3 μm, wherein cover layers on both sides can be of the same or different thicknesses.

Preferred embodiments of the multilayer film are four or five layers. The structure, thickness and composition of a second intermediate or cover layer can be selected independently of the existing matt intermediate layer according to the innovation, whereby the second intermediate layer preferably also contains one of the mixtures described above, which, however, does not have to be identical to that of the first intermediate layer. The second cover layer is also selected from those described above, but independently of the existing one.

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To improve the adhesive properties of the cover layer(s), at least one surface of the film is corona- or flame-treated, whereby the corresponding treatment can be carried out on both surfaces and can be the same or different.
5

It was found that when the polyethylenes described above were incorporated into a propylene homopolymer, propylene copolymer or propylene terpolymer intermediate layer, a very homogeneous film appearance with the desired matt characteristics could be achieved. Surprisingly, the matt appearance of the film is retained despite the applied top layer. This result is particularly astonishing because the conventional top layers made of propylene homopolymer, propylene copolymer and propylene terpolymer are glossy to high-gloss. It would therefore have been expected that the matt appearance of the film would be achieved by the glossy top layer.

15 layer is significantly impaired.

In order to further improve certain properties of the polyolefin film according to the innovation, both the base layer and the cover layer(s) can contain additional additives in an effective amount, preferably antiblocking agents and/or antistatic agents and/or lubricants and/or stabilizers and/or neutralizing agents that are compatible with the propylene polymers of the base layer and the cover layer(s). All quantities given in the following in percent by weight (wt. %) refer to the layer or layers to which the additive can be added.

Suitable antiblocking agents are inorganic additives such as silicon dioxide, calcium carbonate, magnesium silicate, aluminum silicate, calcium phosphate and the like and/or incompatible organic polymers such as polyamides, polyesters, polycarbonates and the like, preference being given to benzoguanamine-formaldehyde polymers, silicon dioxide and calcium carbonate. The effective

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The amount of antiblocking agent is in the range from 0.1 to 2% by weight, preferably 0.1 to 0.5% by weight. The average particle size is between 1 and 6 μπι, in particular 2 and 5 μπι, with particles having a spherical shape, as described in EP-A-236 945 and DE-A-38 01 535, being particularly suitable. The antiblocking agents are preferably added to the cover layers.

Preferred antistatic agents are alkali alkanesulfonates, polyether-modified, ie ethoxylated and/or propoxylated polydiorganosiloxanes (polydialkylsiloxanes, polyalkylphenylsiloxanes and the like) and/or the essentially straight-chain and saturated aliphatic tertiary amines with an aliphatic radical with 10 to 20 carbon atoms which are substituted with 6c-hydroxy-(C ₁ -C ₄ )-alkyl groups, with N,N-bis-(2-hydroxyethyl)-alkylamines with 10 to 20 carbon atoms, preferably 12 to 18 carbon atoms, in the alkyl radical being particularly suitable. The effective amount of antistatic agent is in the range from 0.05 to 0.5% by weight. Furthermore, glycerol monostearate is preferably used as an antistatic agent in an amount of 0.03% to 0.2%.

Lubricants are higher aliphatic acid amides, higher aliphatic acid esters, waxes and metal soaps as well as polydimethylsiloxanes. The effective amount of lubricant is in the range of 0.1 to 3% by weight. The addition of higher aliphatic acid amides in the range of 0.15 to 0.25% by weight in the base layer and/or the top layers is particularly suitable. A particularly suitable aliphatic acid amide is erucic acid amide.
The addition of polydimethylsiloxanes is preferred in the range of 0.3 to 2.0 wt. %, in particular polydimethylsiloxanes with a viscosity of 10,000 to 1,000,000 mm ² /s. The addition of the polydimethylsiloxanes to one or both cover layers is particularly advantageous.

The usual stabilizing compounds for ethylene, propylene and other &sgr;-olefin polymers can be used as stabilizers.

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The amount added is between 0.05 and 2% by weight. Phenolic stabilizers, alkali/alkaline earth stearates and/or alkali/alkaline earth carbonates are particularly suitable.

Phenolic stabilizers are preferred in an amount of 0.1 to 0.6 wt.%, especially 0.15 to 0.3 wt.%, and with a molecular weight of more than 500 g/mol. Pentaerythrityl tetrakis-3-(3,5-di-tertiarybutyl-4-hydroxyphenyl)propionate or 1,3,5-trimethyl-2,4,6-tris(3,5-di-tertiarybutyl-4-hydroxybenzyl)benzene are particularly advantageous.

Neutralizing agents are preferably calcium stearate and/or calcium carbonate and/or synthetic dihydrotalcite (SHYT) with an average particle size of at most 0.7 μνη, an absolute particle size of less than 10/μm and a specific surface area of at least 40 m ² /g.

The innovation further relates to a process for producing the multilayer film according to the innovation by the coextrusion process known per se.
This process involves coextruding the melts corresponding to the individual layers of the film through a flat die, pulling the film thus obtained onto one or more rollers for solidification, then biaxially stretching (orientating) the film, heat-setting the biaxially stretched film and, if necessary, corona-treating the surface layer intended for corona treatment.

Biaxial stretching (orientation) is generally carried out sequentially, with sequential biaxial stretching, in which stretching is carried out first longitudinally (in the machine direction) and then transversely (perpendicular to the machine direction), being preferred.

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First, as is usual in the coextrusion process, the polymer or polymer mixture of the individual layers is compressed and liquefied in an extruder, whereby any additives and/or fillers added may already be contained in the polymer or polymer mixture. The melts are then simultaneously pressed through a flat die (wide slot die) and the pressed multilayer film is drawn off on one or more take-off rollers, where it cools and solidifies.

The film thus obtained is then stretched lengthwise and transversely to the direction of extrusion, which leads to an orientation of the molecular chains. In the longitudinal direction, the stretching ratio is preferably 4:1 to 7:1 and in the transverse direction, it is preferably 8:1 to 11:1. The longitudinal stretching is expediently carried out using two rollers running at different speeds according to the desired stretch ratio, and the transverse stretching is carried out using an appropriate clamp frame.

The biaxial stretching of the film is followed by its thermosetting (heat treatment), whereby the film is held at a temperature of 140 to 160 ^° C for about 0.5 to 10 seconds. The film is then wound up in the usual way using a winding device.

It has proven particularly advantageous to keep the take-off roller or rollers, by means of which the pressed film is also cooled and solidified, at a temperature of 20 to 100 ^° C, preferably 40 to 60 ^° C, by means of a heating and cooling circuit.

The temperatures at which longitudinal and transverse stretching are carried out can vary within a relatively wide range and depend on the respective composition of the individual layers and the desired properties of the film or the base layer, such as opacity,

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Whiteness, thickness, density, etc. In general, longitudinal stretching is preferably carried out at 120 to 150 ⁰ C and transverse stretching is preferably carried out at 155 to 190 ⁰ C.

If necessary, as mentioned above, after biaxial stretching, one or both surfaces of the film can be corona- or flame-treated using one of the known methods. The treatment intensity is generally in a range of 37 to 42 mN/m, preferably 38 to 40 mN/m.

Corona treatment is best done by passing the foil between two conductor elements that serve as electrodes, with such a high voltage, usually alternating voltage (about 5 to 20 kV and 5 to 30 kHz) being applied between the electrodes that spray or corona discharges can occur. The spray or corona discharge ionizes the air above the foil surface and reacts with the molecules on the foil surface, creating polar inclusions in the essentially non-polar polymer matrix.

For a flame treatment with a polarized flame (cf. US-A-4,622,237), an electrical direct voltage is applied between a burner (negative pole) and a cooling roller. The level of the applied voltage is between 500 and 3,000 V, preferably in the range of 1,500 to 2,000 V. The applied voltage gives the ionized atoms increased acceleration and they hit the polymer surface with greater kinetic energy. The chemical bonds within the polymer molecule are broken more easily, and the formation of radicals takes place more quickly. The thermal load on the polymer is much lower than with standard flame treatment, and films can be obtained in which the sealing properties of the treated side are even better than those of the untreated side.

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The new multi-layer film is characterized by a very homogeneous film appearance and a characteristic matt appearance in combination with very good, consistent surface properties.

The matte appearance of the film creates a paper-like appearance of the film, which is particularly desirable for certain applications in the packaging sector. Surprisingly, it has been shown that not only the minimization of gloss brings the desired optical effect, but that rather a balanced optimization of the properties is required, which is surprisingly possible with the special intermediate layer composition according to claim 1.

Surprisingly, the matte appearance of the film is retained despite the outer, glossy cover layer. In this way, it is possible to combine the matte appearance of the new HDPE-containing layer with the advantageous surface properties of the conventional cover layers. The film has very good machineability and good running properties as well as good sealing properties. The film is very suitable for corona or flame treatment and has excellent printability. In addition, the film is very suitable for covering and laminating due to its good adhesive properties. The film shows little abrasion and good sliding properties.

The film structure with the conventional cover layer and the innovative intermediate layer offers particular advantages in terms of its possible variations. Since, surprisingly, the film appearance is predominantly determined by the intermediate layer, the film manufacturer can now provide the processor with films with very different appearances, while retaining the surface characteristics of the films. For the processor, this means that he can easily switch from one film to another without

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having to change the processing conditions every time. This results in significant economic advantages.

In summary, it can be stated that the multilayer film according to the innovation is characterized by a number of advantageous properties, in particular

&bull; a characteristic matt gloss of less than 80 at a measuring angle of 85° (ASTM-D-523-78),

&bull; a particularly uniform matt film appearance, 10 · good surface properties,

&bull; good long-term stability of the surface tension and

&bull; optical variation options with consistent surface properties.

This surprising variety of excellent properties means that a film is now available that can be used equally well for a wide range of purposes, in particular as an advertising-effective matt laminating film or as an opaque packaging film on high-speed packaging machines or as an opaque cigarette wrapping film or as an opaque film for the labeling process such as in-mold labeling.

In addition, the film is excellent for use as a carrier film for adhesive tapes (long-term stability, high surface tension) or as a carrier film for aqueous barrier coating systems, e.g. based on aqueous dispersions of polyvinylidene chloride or ethylene-vinyl alcohol copolymers.

It can be printed with aqueous printing inks for various purposes and has excellent short- and long-term printability. Due to its good immediate and long-term coating properties, the film is also suitable for the production of plastic labels, especially those used in the in-mold labeling process. The film is also suitable for the production of

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of laminates with paper, cardboard, metals, metallized plastic films and plastic films.

The innovation will now be explained in more detail using examples. 5

example 1

According to the coextrusion process, a 1.4 mm thick four-layer film with a layer structure ABCD was extruded from a slot die at an extrusion temperature of 260 ⁰ C, ie an intermediate layer C was applied to one surface of the base layer B and a cover layer A was applied to the other surface of the base layer B. A cover layer D different from A was applied to the intermediate layer C. The cover layer D was corona treated.

15 The main components of the base layer were:

92.6 wt.% propylene homopolymer (PP) with an n-heptane-soluble

A proportion of 4.5 wt.% (based on 100% PP) and a

Melting point of 165 ⁰ C; the melt flow index of the product

pylene homopolymers is 3.2 g/10 min at 230 ⁰ C and

20 21.6 N load (DIN 53 735);

4.2 wt.% CaCO ₃ of the type ®Omyalithe 90T ₁ Supplier of masterbatches

Company Multibase, Z.I. du Giers, F-38380 Saint-Laurent-du-Pont, France;

3.2 wt.% TiO ₂ via Masterbatch ®P 8555 LM, supplier company

Schulman GmbH, Hüttenstrasse 211, D-5014 Kerpen 3

The intermediate layer C consisted of a mixture of two mixture components I and II. Component I was a terpolymer of ethylene, propylene and butylene-1 units with an ethylene content of 1.9 wt.% and a butylene-1 content of 8.4 wt.%, based on the terpolymer. The melt flow

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index (21.6 N/230 ⁰ C) was 6.5 g/10 min. Component II was a HDPE with an MFI (50 N/190 ⁰ C) of 11 g/10 min (measured according to DIN 53 735), a viscosity number of 160 cm ³ /g (measured according to DIN 53 728, Part 4), a density of 0.954 g/cm ³ (measured according to DIN 53 479, method A), a degree of crystallization of 68% and a melting point of 132 ⁰ C according to DSC measurement. The proportion of both mixture components I and II in the composition of the intermediate layer was 50 wt.% each.

Before processing in the extruder, both components were mechanically mixed in a ratio of 1:1 for 2 minutes at 500 rpm in a Henschel mixer to produce a homogeneous granulate mixture.

The top layer D consisted of a terpolymer of ethylene, propylene and butylene-1 units with an ethylene content of 1.9 wt.% and a butylene-1 content of 8.4 wt.%, based on the terpolymer. The melt flow index (21.6 N/230 ⁰ C) was 6.5 g/10 min.

The top layer A consisted of a random ethylene-propylene copolymer with an ethylene content of 5 wt.%, based on the weight of the copolymer. The melting point of the copolymer was 134 ⁰ C, and the melt flow index (21.6 N/230 ⁰ C) was 7.0 g/10 min.

All layers contained 0.12% by weight of pentaerythrityl tetrakis-4-(3,5-ditertiarybutyl-4-hydroxyphenyl) propionate (®lrganox 1010) for stabilization and 0.06% by weight of calcium stearate as a neutralizing agent. The base layer also contained 0.15% by weight of N,N-bis(2-hydroxyethyl)-(C ₁₀ -C ₂₀ )-alkylamine (®Armostat 300) as an antistatic agent.

The extruded four-layer film was processed through the corresponding process steps after coextrusion via a first take-off roll and a further roll trio

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stripped and cooled, then stretched lengthwise, stretched crosswise, fixed and corona treated, whereby the following conditions were chosen in detail:

Extrusion:

Longitudinal stretch: Transverse stretch:

Fixation: Corona treatment:

Extrusion temperature 260 ⁰ C Temperature of the first take-off roll 50 ⁰ C Temperature of the roll trio 50 ⁰ C Stretching roll T = 125 ⁰ C Longitudinal stretching by a factor of 5 Heating fields T = 175 ⁰ C Stretching fields T = 165 ⁰ C Transverse stretching by a factor of 10 Temperature T = 155 ⁰ C Voltage: 10 000 V Frequency: 10 000 Hz

The multilayer film produced in this way had a surface tension of 40 to 41 mN/m (D side) immediately after production. The film was approximately 28 μm thick, with the thickness of the cover layer A and the cover layer D being approximately 0.9 μm, that of the intermediate layer C being approximately 3.5 μm and that of the base layer being 22.7 μm.

Example 2

Example 1 was repeated. Only the composition of the intermediate layer C was modified as follows:

70 wt.% of the terpolyester used in Example 1 in the intermediate layer C

more
30 wt.% of the HDPE used in Example 1 in the intermediate layer C

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Example 3

Example 1 was repeated. The composition of the intermediate layer C was modified as follows:

50 wt.% of the copolymer used in Example 1 in the top layer A 50 wt.% of the HDPE used in Example 1 in the intermediate layer C

The composition of the top layer D was modified as follows:

100 wt.% of the copolymer used in top layer A in Example 1.

10 Example 4

Example 3 was repeated. Only the composition of the intermediate layer C

was modified as follows:

30 wt.% of the HDPE used in Example 1 in the intermediate layer C

70 wt.% of the copolymer used in Example 1 in the top layer A 15

Example 5

Example 3 was repeated. Only the composition of the intermediate layer C

was modified as follows:

30 wt.% of the HDPE used in Example 1 in the intermediate layer C
70 wt.% of the homopolymer used in Example 1 in base layer B

Example 6

Example 5 was repeated. Only the composition of the top layer D was modified as follows:
100 wt.% of the homopolymer used in the base layer in Example 1

Example 7

Example 1 was repeated. Only the composition of the intermediate layer C was modified as follows:
30

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43.7 wt.% of the intermediate layer C used in Example 1

Terpolymers

43.7 wt.% of the intermediate layer C used in Example 1

HDPE
7.0 wt.% of the TiO ₂ used in Example 1 in the base layer B

5.6 wt.% of the poly used in Example 1 in the base layer B

propylene.

Example 8

Example 1 was repeated. Only the composition of the intermediate layer C

was modified as follows:

47.5 wt.% of the intermediate layer C used in Example 1

Terpolymers

47.5 wt.% of the intermediate layer C used in Example 1

15 HDPE

5.0 wt.% of the CaCO ₃ used in Example 1 in base layer B

Example 9

Example 1 was repeated. Only the composition of the intermediate layer C was modified as follows:

46.3 wt.% of the terpolymer used in Example 1 in the top layer D
46.3 wt.% of the intermediate layer C used in Example 1

HDPE

4.2 wt.% of the CaCO ₃ used in Example 1 in base layer B

3.2 wt.% of the TiO ₂ used in Example 1 in the base layer B

Example 10

Example 1 was repeated. Only the composition of base layer B was modified as follows:

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95 wt.% of the homopolymer used in Example 1 in the base layer B 5 wt.% of the CaCO ₃ used in Example 1 in the base layer B

Example 11

Example 1 was repeated. Only the composition of base layer B was modified as follows:

92 wt.% of the homopolymer used in Example 1 in the base layer B 8 wt.% of the TiO ₂ used in Example 1 in the base layer B

10 Comparison example 1

Example 7 was repeated, but as a three-layer film without cover layer D.

Comparison example 2

Example 8 was repeated, but as a three-layer film without cover layer D.
15

Comparison example 3

Example 1 was repeated, but as a three-layer film without intermediate layer C.

The following measurement methods were used to characterize the raw materials and the films:

Melt flow index

The melt flow index was measured in accordance with DIN 53 735 at 21.6 N load and 230 ⁰ C or at 50 N load and 190 ⁰ C.
25

Melting point

DSC measurement, maximum of the melting curve, heating rate 20 °C/min.

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Viscosity number J

The viscosity number is a measure of the molar mass. The viscosity number is measured according to DIN 53 728, Part 4, in 0.1% decahydronaphthalene solution at 135 ⁰ C.
5

Density &sgr;

The density is determined according to DIN 53 479, method A.

Degree of crystallization a
The degree of crystallization can be determined by the following relationship:

amorphous 4&lgr;&lgr;&eegr;/

OC - ' IUU /&ogr;

^&sgr; crystalline ~ ^{α amorphous}

with <r _amorphous = 0.8549 g/cm ³

o- _crystalline = 1.0005 g/cm ³

Crystalline * w/

σ = density of the HDPE type used

shine

The gloss was determined according to DIN 67 530. The reflector value was measured as an optical parameter for the surface of a film. Based on the standards ASTM-D 523-78 and ISO 2813, the angle of incidence was set at 60° or 85°

20. A light beam hits the flat test surface at the set angle of incidence and is reflected or scattered by it. The light rays striking the photoelectric receiver are displayed as a proportional electrical quantity. The measured value is dimensionless and must be specified with the angle of incidence.

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Seal seam strength

For the determination, two 15 mm wide film strips were placed on top of each other and sealed at 130 ^° C, a sealing time of 0.5 s and a sealing pressure of 10 N/cm ² (device: Brugger type NDS, one-sided heated sealing jaw). The seal seam strength was determined using the T-peel method.

Roughness

The roughness was determined according to DIN 4768.

10 Friction

The friction was determined in accordance with DIN 53 375.

Surface tension

The surface tension was determined using the so-called ink method (DIN 53 364).

Printability

The corona-treated films were printed 14 days after their production (short-term assessment) or 6 months after their production (long-term assessment). The ink adhesion was assessed using an adhesive tape test. If only a small amount of ink could be removed using adhesive tape, the ink adhesion was rated as moderate, and if the ink was clearly removed, it was rated as poor.

Water vapor barrier

The water vapor barrier is measured in accordance with DIN 53 122 at 23 ⁰ C and 85 % relative humidity and indicates the amount of water that passes through per square meter and day in grams.

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Opacity and White Wheel

The opacity and the degree of whiteness are determined using the electrical remission photometer "ELREPHO" from Zeiss, Oberkochem (DE), standard illuminant C, 2° standard observer. The opacity is determined according to DIN 53 146. The degree of whiteness is defined as WG = RY + 3RZ - 3RX.

WG = degree of whiteness; RY, RZ, RX = corresponding reflection factors when using the Y, Z and X color measuring filters. A pressed piece of barium sulfate (DIN 5033, Part 9) is used as the white standard. A detailed description is given, for example, in Hansl Loos, "Farbmessung", Verlag Beruf und Schule, Itzehoe, 1989.

Light transmission

The light transmittance is measured according to ASTM-D 1003-77.

The properties and structure of the polypropylene multilayer films of the examples and comparative examples are summarized in Tables 1 and 2 below.

TABLE 1

Example Base layer B Intermediate layer C Top layer A Top layer D B1 92.6 wt.% PP; 4.2 wt.% CaCO ₃ ;
3.2 wt.% TiO ₂ 50 wt% terpolymer; 50 wt% HDPE 100 wt.% copolymer 100 wt.% terpolymer B2 like example 1 70 wt% terpolymer; 30 wt% HOPE 100 wt.% copolymer 100 wt.% terpolymer B3 like example 1 50 wt% copolymer; 50 wt% HOPE 100 wt.% copolymer 100 wt.% copolymer B4 like example 1 70 wt% copolymer; 30 wt% HDPE 100 wt.% copolymer 100 wt.% copolymer B5 like example 1 70 wt% homopolymer; 30 wt% HDPE 100 wt.% copolymer 100 wt.% copolymer B6 like example 1 70 wt% homopolymer; 30 wt% HDPE 100 wt.% copolymer 100 wt.% homopolymer
(not sealable) B7 like example 1 43.7 wt% terpolymer; 43.7 wt% HDPE;
7.0 wt.% TiO ₂ ; 5.6 wt.% PP 100 wt.% copolymer 100 wt.% terpolymer B8 like example 1 47.5 wt.% terpolymer; 47.5 wt% HOPE
5.0 wt.% CaCO ₃ 100 wt.% copolymer 100 wt.% terpolymer B9 like example 1 46.3 wt% terpolymer; 46.3 wt% HDPE;
4.2 wt.% CaCO ₃ ; 3.2 wt.% TIO ₂ 100 wt.% copolymer 100 wt.% terpolymer B10 95 wt% PP; 5 wt% CaCO ₃ 50 wt% Teφolymer; 50 wt% HOPE 100 wt.% copolymer 100 wt.% terpolymer B11 92 wt% PP; 8 wt% TiO, 50 wt% terpolymer; 50 wt% HDPE 100 wt.% copolymer 100 wt.% terpolymer VB1 like example 1 100 wt.% copolymer 43.7 wt.% terpolymer;
43.7 wt% HDPE;
7.0 wt.% TiO ₂ ;
5.6 wt.% PP VB2 like example 1 100 wt.% copolymer 47.5 wt.% terpolymer;
47.5 wt% HDPE;
5.0 wt.% CaCO ₃ VB3 like example 1 100 wt.% copolymer 100 wt.% terpolymer

CD m cn m

B = example; VB « comparison example

Result; VB1 "chalks" on rollers

VB2 "chalks" on rollers and absorbs a lot of paint!

TABLE 2

Example shine Friction visual assessment + + Whiteness opacity density Print image coefficient (matte appearance + + D-side D-side picture) + + 85°, D-ropes + + B1 45 0.6 + + 74 69 0.78 + + B2 47 0.5 + + 74 69 0.78 + + B3 50 0.5 + + 75 70 0.78 + + B4 52 0.5 + + 74 69 0.77 + + B5 53 0.6 + + 74 69 0.78 + + B6 55 0.5 + + 74 69 0.78 + + B7 40 0.4 + + 77 70 0.80 + + B8 38 0.5 + + 76 70 0.78 + + B9 40 0.5 + + 79 73 0.79 + + B10 45 0.5 -- 65 67 0.69 + + B11 45 0.6 81 64 0.94 + + VB1 34 0.5 77 70 0.78 - VB2 29 0.5 75 70 0.78 + VB3 84 0.5 77 70 0.78 + +

B « example; VB = comparative example

Claims (34)

HOECHST AKTIENGESELLSCHAFT Plant KALLE-ALBERT 93/K034G -44- 17.5.1993 WL-DC. Fa-bl Protection claims 1. Opaque polypropylene multilayer film, which comprises at least one base layer, containing polypropylene or a polypropylene mixture and fillers, and at least one intermediate layer and at least one cover layer applied to this intermediate layer, wherein the cover layer essentially a propylene homopolymer or a copolymer of 10 Ethylene and propylene or Ethylene and butylene or propylene and butylene or ethylene and another &sgr;-olefin having 5 to 10 carbon atoms or Propylene and another &sgr;-olefin with 5 to 10 carbon atoms men or
a terpolymer of Ethylene and propylene and butylene or ethylene and propylene and another &sgr;-olefin having 5 to 10 carbon atoms or a mixture of two or more of the above-mentioned homo-, co- and terpolymers or a blend of two or more of the above-mentioned homo-, co- and terpolymers, optionally mixed with one or more of the above-mentioned homo-, co- and terpolymers, and the intermediate layer contains a mixture or a blend of two components I and II, characterized in that component I essentially a propylene homopolymer or HOECHST AKTIENGESELLSCHAFT Plant KALLE-ALBERT 93/K 034G - 45 - a copolymer of Ethylene and propylene or ethylene and butylene or propylene and butylene or 5 ethylene and another a-olefin with 5 to 10 carbon atoms or Propylene and another &sgr;-olefin having 5 to 10 carbon atoms or a terpolymer of
Ethylene and propylene and butylene or Ethylene and propylene and another a-olefin having 5 to 10 carbon atoms or a mixture of two or more of the above-mentioned homo-, co- and terpolymers or 15 a blend of two or more of the above-mentioned homo-, co- and terpolymers, optionally mixed with one or more of the above-mentioned homo-, co- and terpolymers,
contains and Component II essentially
a HDPE or a blend of two blend components A and B, wherein the blend component A is essentially is a HDPE and the blend component B is essentially a propylene homopolymer or a copolymer of Ethylene and propylene or ethylene and butylene or propylene and butylene or HOECHST AKTIENGESELLSCHAFT Plant KALLE-ALBER1 93/K 034G - 46 - Ethylene and another &sgr;-olefin having 5 to 10 carbon atoms or Propylene and another &sgr;-olefin having 5 to 10 carbon atoms or
a terpolymer of Ethylene and propylene and butylene or
Ethylene and propylene and another &sgr;-olefin having 5 to 10 carbon atoms or a mixture of two or more of the above-mentioned homo-, co- and terpolymers or a blend of two or more of the above-mentioned homo-, co- and terpolymers
is and the film is matt. 15 2. Polypropylene multilayer film according to claim 1, characterized in that
Component I essentially a propylene homopolymer or 20 a copolymer of Ethylene and propylene or ethylene and butylene-1 or propylene and butylene-1 or a terpolymer of 25 ethylene and propylene and butylene-1 or a mixture of two or more of the particularly preferred homo-, co-terpolymers or a blend of two or more of the particularly preferred homo-, co- and terpolymers mentioned, optionally mixed with one or HOECHST AKTIENGESELLSCHAFT KALLE-ALBERT plant
93/K 034G - 47 - several of the above-mentioned homo-, co- and terpolymers, in particular propylene homopolymer or statistical ethylene-propylene copolymers with an ethylene content of 2 to 10 wt.%, preferably 5 to 58 wt.%, or statistical propylene-butylene-1 copolymers with a butylene content of 4 to 25 wt.%, preferably 10 to 20 wt.%, each based on the total weight of the copolymer, or 10 statistical ethylene-propylene-butylene-1 terpolymers with an ethylene content of 1 to 10 wt.%, preferably 2 to 6 wt.%, and a butylene-1 content of 3 to 20 wt.%, preferably 8 to 10 wt.%,
15 each based on the total weight of the terpolymer, or a blend of an ethylene-propylene-butylene-1 terpolymer and a propylene-butylene-1 copolymer with an ethylene content of 0.1 to 7 wt.% 20 and a propylene content of 50 to 90 wt.% and a butylene-1 content of 10 to 40 wt.%,
each based on the total weight of the polymer blend, are preferred, and the blend component B is essentially a propylene homopolymer or a copolymer of Ethylene and propylene or ethylene and butylene-1 or propylene and butylene-1 or HOECHST AKTIENGESELLSCHAFT Plant KALLE-ALBERT 93/K 034G - 48 - a terpolymer of Ethylene and propylene and butylene-1 or a mixture of two or more of the particularly preferred homo-, co- and terpolymers mentioned or a blend of two or more of the above-mentioned particularly preferred Homo-, co- and terpolymers,
in particular propylene homopolymer or statistical ethylene-propylene copolymers with an ethylene content of 2 to 10 wt.%, preferably 5 to 8 wt.%, or statistical propylene-butylene-1 copolymers with a butylene content of 4 to 25 wt.%, preferably 10 to 20 wt.%, each based on the total weight of the copolymer, or statistical ethylene-propylene-butylene-1 terpolymers with an ethylene content of 1 to 10 wt.%, preferably 2 to 6 wt.%, and a butylene-1 content of 3 to 20 wt.%, preferably 8 to 10 wt.%,
each based on the total weight of the terpolymer, or a blend of an ethylene-propylene-butylene-1 terpolymer and a propylene-butylene-1 copolymer with an ethylene content of 0.1 to 7 wt.% 25 and a propylene content of 50 to 90 wt.% and a butylene-1 content of 10 to 40 wt.%,
each based on the total weight of the polymer blend, are preferred. HOECHST AKTIENGESELLSCHAFT Plant KALLE-ALBERT 93/K 034G - 49 - 3. Polypropylene multilayer film according to claim 1 and/or 2, characterized in that the HDPE has an MFI (50 N/190 ⁰ C) of greater than 1 to 50 g/10 min (measured according to DIN 53 735), a viscosity number of 100 to 450 cm ³ /g (measured according to DIN 53 728, part 4), a density of 0.93 to 0.97 g/cm ³ (measured according to DIN 53 479, method A), a degree of crystallization of 35 to 80% and a melting point of 120 to 150 ⁰ C according to DSC measurement. 4. Polypropylene multilayer film according to one or more of claims 1 to 3, characterized in that the ratio of the blend components A and B is in the range from A:B = 20:80 to A:B = 80:20, preferably between A:B = 40:60 and A:B = 60:40. 5. Polypropylene multilayer film according to one or more of claims 1 to 4, characterized in that the blend has a melt flow index of 1.5 to 12 g/10 min, preferably 2.5 to 6 g/10 min, (230 ⁰ C, 21.6 N load). 6. Polypropylene multilayer film according to one or more of claims 1 to 5, characterized in that the ratio of the components I and Il are in the range of l:ll = 90:10 to l:ll = 10:90. 7. Polypropylene multilayer film according to one or more of claims 1 to 6, characterized in that the propylene polymer of the base layer has a melting point of at least 140 ^° C and the melt flow index is in the range from 0.5 to 15 g/10 min. 8. Polypropylene multilayer film according to one or more of claims 1 to 7, characterized in that the base layer contains fillers HOECHST AKTIENGESELLSCHAFT Plant KALLE-ALBERT 93/K 034G - 50 - contains vacuole-initiating solid particles and/or pigments. 9. Polypropylene multilayer film according to claim 8, characterized in that the solid particles have an average particle diameter of >1//m and the pigments have an average particle diameter of <1/vm. 10. Polypropylene multilayer film according to claim 8 and/or 9, characterized in that the solid particles are CaCO ₃ or incompatible polymers 10 and the pigments are TiO ₂ . 11. Polypropylene multilayer film according to one or more of claims 1 to 10, characterized in that the base layer contains as fillers only pigments, preferably TiO ₂ , in an amount of 2 to 25 wt.%. 12. Polypropylene multilayer film according to one or more of claims 1 to 10, characterized in that the base layer contains as fillers only solid particles, preferably CaCO ₃ , in an amount of 1 to 25 wt.%. 13. Polypropylene multilayer film according to claim 12, characterized in that the solid particles are contained in the base layer in an amount of 2 to 5 wt.%. 14. Polypropylene multilayer film according to claim 12, characterized in that the base layer contains the solid particles in an amount of 9 to 14% by weight. HOECHST AKTIENGESELLSCHAFT Plant KALLE-ALBERT 93/K 034G - 51 - 15. Polypropylene multilayer film according to one or more of claims 1 to 10, characterized in that the base layer contains as fillers solid particles, preferably CaCO ₃ , in an amount of 1 to 10 wt.% and pigments, preferably TiO ₂ , in an amount of 1 to 7 wt.%. 16. Polypropylene multilayer film according to one or more of claims 1 to 11, characterized in that the density of the film is >0.9 g/cm ³ . 17. Polypropylene multilayer film according to one or more of claims 1 to 10 and 12, characterized in that the density of the film is 0.4 to 0.85 g/cm ³ . 18. Polypropylene multilayer film according to one or more of claims 1 to 10 and 13, characterized in that the density of the film is 0.7 up to 0.85 g/cm ³ . 19. Polypropylene multilayer film according to one or more of claims 1 to 10 and 14, characterized in that the density of the film is 0.4 20 to 0.7 g/cm ³ . 20. Polypropylene multilayer film according to one or more of claims 1 to 10 and 15, characterized in that the density of the film is 0.6 to 0.85 g/cm ³ . 21. Polypropylene multilayer film according to one or more of claims 1 to 20, characterized in that the intermediate layer contains solid particles and/or pigments as fillers. HOECHST AKTIENGESELLSCHAFT KALLE-ALBERT plant
93/K 034G - 52 - 22. Polypropylene multilayer film according to one or more of claims 1 to 20, characterized in that the intermediate layer is essentially vacuole-free. 23. Polypropylene multilayer film according to one or more of claims 1 to 20, characterized in that the intermediate layer contains only solid particles, preferably CaCO ₃ or SiO ₂ in an amount of 1 to 25 wt.%. 24. Polypropylene multilayer film according to one or more of claims 1 to 20, characterized in that the intermediate layer contains only pigments, preferably TiO ₂ , in an amount of 2 to 25 wt.%. 25. Polypropylene multilayer film according to one or more of claims 1 to 20, characterized in that the intermediate layer contains solid particles, preferably CaCO ₃ or SiO ₂ , in an amount of 1 to 20 wt.% and pigments, preferably TiO ₂ , in an amount of 1 to 20 wt.%. 26. Polypropylene multilayer film according to one or more of claims 1 to 25, characterized in that the cover layer is essentially a propylene homopolymer or a copolymer of Ethylene and propylene or Ethylene and butylene-1 or 25 Propylene and butylene-1 or a terpolymer of Ethylene and propylene and butylene-1 or a mixture of two or more of the particularly preferred homo-, co-terpolymers or HOECHST AKTIENGESELLSCHAFT KALLE-ALBERT plant
93/K 034G - 53 - a blend of two or more of the particularly preferred homo-, co- and terpolymers mentioned, optionally mixed with one or more of the homo-, co- and terpolymers mentioned,
in particular propylene homopolymer or
statistical ethylene-propylene copolymers with an ethylene content of 2 to 10 wt.%, preferably 5 to 8 wt.%, or
statistical propylene-butylene-1 copolymers with a butylene content of 4 to 25 wt.%, preferably 10 to 20 wt.%, each based on the total weight of the copolymer, or statistical ethylene-propylene-butylene-1 terpolymers with an ethylene content of 1 to 10 wt.%, preferably 2 to 6 wt.%, and a butylene-1 content of 3 to 20 wt.%, preferably 8 up to 10 wt.%, each based on the total weight of the terpolymer, or a blend of an ethylene-propylene-butylene-1 terpolymer and a propylene-butylene-1 copolymer with an ethylene content of 0.1 to 7 wt.%
and a propylene content of 50 to 90 wt.%
and a butylene-1 content of 10 to 40 wt.%,
each based on the total weight of the polymer blend, are preferred. 27. Polypropylene multilayer film according to one or more of claims 1 to 26, characterized in that the cover layer and/or the HOECHST AKTIENGESELLSCHAFT Plant KALLE-ALBERT 93/K 034G - 54 - Base layer contains as additives antiblocking agents and/or antistatic agents and/or lubricants and/or stabilizers and/or neutralizing agents. 28. Polypropylene multilayer film according to claim 1, characterized in that it has a gloss of less than 80, preferably 25 to 65, on the two matt side(s) at a measuring angle of 85°, measured according to ASTM-D 523-78. 29. Polypropylene multilayer film according to one or more of claims 1 to 28, characterized in that one, optionally both Surface(s) is/are provided with a print. 30. Polypropylene multilayer film according to one or more of claims 1 to 28, characterized in that one or both surfaces 15 contains/contains an adhesive layer, possibly partially. 31. Laminates containing a polypropylene multilayer film according to one or more of claims 1 to 28. 32. Packaging containing a polypropylene multilayer film according to one or more of claims 1 to 28. 33. Coated barrier systems containing a polypropylene multilayer film according to one or more of claims 1 to 28. 34. Label comprising a polypropylene multilayer film according to one or more of claims 1 to 28.