DE102023120083A1 - film with increased water vapor permeability - Google Patents

Abstract

The invention relates to a plastic film (1) comprising at least one layer (2, 3). The at least one layer (2) consists essentially of ethylene vinyl acetate (EVA), the ethylene vinyl acetate (EVA) having a vinyl acetate (VA) content of at least 15% by weight to ensure a water vapor diffusion-equivalent air layer thickness (s _d value) of less than 15 m. The at least one layer (2, 3) has a content of at least 5% by weight of polylactide (PLA).

Description

The invention relates to a plastic film comprising at least one layer.

In the construction sector, very diffusion-open materials are generally preferred for the external insulation of buildings in order to dissipate moisture that has penetrated and/or residual moisture from the building materials to the outside.

In general, according to the state of the art, single-sided adhesive tapes are usually used for bonding films in house construction, which in particular have films based on polyethylene, PVC or thermally compacted spunbonded carriers.

The EP 1 847 577 B1 describes an adhesive tape with a film carrier made of ethylene vinyl acetate (EVA) and ether ester block copolymer (TPE-E) for the diffusion-open bonding of roofing membranes above the insulation layer. In addition to a low s _d value of ∼ 12 m, a special elongation behavior is highlighted as important. A difference value between the percentage total elongation under load and the percentage remaining elongation after load is described as a characteristic parameter.

In the DE 20 2010 014 075 U1 a technical adhesive tape is disclosed, in particular for bonding films or nonwovens in the construction sector, with a band-shaped carrier made of plastic and with a pressure-sensitive adhesive coating made of a pressure-sensitive adhesive applied to at least one side, which is applied with a basis weight of at least 100 g/m ^2. The carrier comprises a cast polyolefin film which is elastically and plastically stretchable to such an extent that a difference value between the percentage total elongation under load and the percentage permanent elongation after subsequent unloading is in the range of 15 to 50%.

There are already adhesive tapes with elastic properties, but they usually do not offer sufficient rigidity to permanently and reliably bond films under tension.

The object of the present invention is to provide a plastic film that has a good sealing effect and at the same time good water vapor permeability. The plastic film should be suitable for fixing construction films, in particular films in the area of the building envelope. In addition, the plastic film should be able to have a sufficiently high tension and good rigidity when glued.

This object is achieved according to the invention by a plastic film, a method and a use according to the independent main claims. Preferred variants can be found in the subclaims, the description, the exemplary embodiment and the drawing.

According to the invention, the at least one layer consists essentially of ethylene-vinyl acetate (EVA), wherein the ethylene-vinyl acetate (EVA) has a proportion of vinyl acetate (VA) of at least 15% by weight, to ensure a water vapor diffusion equivalent air layer thickness (s _d value) of less than 15 m and at least one layer has a proportion of at least 5% by weight of polylactide (PLA).

The s _d value is important in building physics, especially when planning buildings and selecting building materials. It influences the moisture regulation in a building and can have an impact on the indoor climate and energy efficiency. For example, a vapor barrier that is too high or an inadequate vapor barrier can lead to moisture problems such as mold formation.

The s _d value represents the water vapor diffusion resistance of a building material or component. It is a unit of measurement that indicates how well a material prevents the passage of water vapor. The s _d value is given in meters.

A low s _d value means that a material is vapor permeable and can allow water vapor to pass through relatively easily. A high S _d value, on the other hand, indicates that a material is vapor-tight and severely impedes or even prevents the passage of water vapor.

DIN 52615 is a German standard entitled "Determination of the water vapor diffusion resistance and the moisture content of building materials - climate chamber method". This standard specifies a method for determining the water vapor diffusion resistance (s _d value) and the moisture content of building materials.

The climate chamber method, which is described in DIN 52615, enables the water vapor diffusion resistance of a building material to be measured by exposing the building material to a defined humidity and temperature in a climate chamber. The water vapor diffusion resistance can be calculated by measuring the moisture content of the building material before and after exposure.

For example, the s _d value of the plastic film is less than 8m, preferably less than 5m, in particular less than 2 m and is thus ideally suited to ensure the required water vapor permeability.

In an advantageous embodiment of the invention, the s _d value of the plastic film is less than 1.2 m.

As an alternative to the s _d value, the water vapor permeability can be determined according to DIN 53116 using a gravimetric measuring method. A test container filled with a desiccant is sealed with a plastic film and exposed to a defined test climate. The amount of water permeating through the sample is determined by weighing. A water quantity in a range of 1-200 g/(m ² · d) can be detected. The detection limit also depends on the sample properties and thickness.

For example, the plastic film has a water vapor permeability rate of more than 20 g/(m ² · d), preferably more than 25 g/(m ² · d), in particular more than 30 g/(m ² · d) according to DIN 53116 and is therefore ideally suited as a plastic film for adhesive tapes.

The advantageous water vapor permeability is achieved, for example, by using ethylene vinyl acetate (EVA). In one embodiment of the invention, the proportion of ethylene vinyl acetate (EVA) in the at least one layer is more than 90% by weight, preferably more than 95% by weight, in particular more than 97.5% by weight.

Ethylene vinyl acetate (EVA) is a copolymer made from the monomers ethylene, vinyl acetate and optionally other co-monomers. It is a thermoplastic material with a wide range of applications.

Ethylene-vinyl acetate (EVA) is known for its flexible nature and good processability. It can be easily melted and formed into various shapes such as films and coatings. The properties of ethylene-vinyl acetate (EVA), especially water vapor permeability and stickiness, can be specifically adjusted using the proportion of vinyl acetate monomer. In addition, ethylene-vinyl acetate (EVA) is particularly characterized by its good weather resistance, its electrical insulating properties and its transparency for certain wavelengths of light.

For example, at least one layer can consist almost entirely of ethylene vinyl acetate (EVA) and thus realize the water vapor permeability according to the application in construction.

The proportion of vinyl acetate (VA) of the ethylene vinyl acetate (EVA) is, for example, more than 20% by weight, preferably more than 25% by weight and/or less than 50% by weight, preferably less than 40% by weight, in order to achieve favorable water vapor permeability.

Vinyl acetate is a monomer and belongs to the group of vinyl compounds. It consists of a vinyl residue and an acetate residue. An important use of vinyl acetate is the production of ethylene-vinyl acetate (EVA). The copolymerization of vinyl acetate with ethylene produces EVA, a flexible and water vapor-permeable material.

Optionally, the plastic film has a thickness of more than 40 µm, preferably more than 50 µm, in particular more than 60 µm and/or less than 120 µm, preferably less than 105 µm, in particular less than 90 µm. This results in a good feel and a stable band for robust applications.

At the same time, the plastic film has a desirable tension in addition to the advantageous water vapor permeability.

Films and sheets with a thickness of up to 1 mm are tested using strip or shoulder specimens. According to ISO 527-3 and ASTM D 882, the usual specimen shape is strip. This specimen shape can be easily produced using a cutting press or a film cutting device. Shoulder specimens are often used in quality control. In this case, a direct measuring extensometer is required with which the specimen strains can be recorded directly on the specimen. Typical test results such as the yield stress, yield strain, maximum stress and nominal elongation at break are recorded.

The tensile properties are determined according to DIN EN ISO 527. In the tensile test, a sample strip of a plastic film is stretched at a constant speed specified in the test standard and the force F is recorded with the change in length ΔL of the measuring section L ₀ .

In one embodiment of the invention, the plastic film has a stress of more than 2 MPa, preferably more than 3 MPa, in particular more than 4 MPa according to DIN EN ISO 527-3 at 5% elongation. This makes the plastic film particularly stiff and tough, which means that the necessary stress can be achieved as a plastic film, for example in the form of an adhesive tape.

For example, the plastic film is designed as a monolayer film and has a rather low thickness.

At least one layer of the monofilm contains at least 5% by weight of polylactide (PLA). The PLA reduces the stickiness of the film, which is beneficial for processing and application.

In one variant, the plastic film contains more than 10% by weight, preferably more than 15% by weight, in particular more than 20% by weight of polylactide (PLA). This monofilm has a very low thickness with increased rigidity. The PLA content increases the rigidity enormously, which means that a structural layer can be dispensed with, for example.

In an exemplary embodiment of the invention, the at least one layer has a proportion of at least 5 wt.% polybutylene adipate terephthalate (PBAT).

In further variants of the invention, the plastic film can also be designed as a two-layer, three-layer, five-layer or seven-layer film.

The desired rigidity can be supported, for example, by combining the at least one layer with another layer. For this purpose, the plastic film comprises at least one further layer.

For example, the at least one layer is surrounded by another layer and the plastic film is thus formed in a sandwich arrangement. The plastic film, as a three-layer film with a thick central layer and a thin outer layer, has particularly good properties with regard to s _d value, water vapor permeability and tension.

In an exemplary embodiment of the invention, the further layer has a proportion of at least 5 wt.% polylactide (PLA).

Polylactide (PLA) stands for polylactic acid. Polylactide is biodegradable, which means it can be broken down by microorganisms or enzymes into natural compounds such as carbon dioxide and water. This allows for more environmentally friendly disposal compared to traditional plastics. Polylactide is derived from plant sources such as corn starch, sugar cane or other sugar crops. Compared to petroleum-based plastics, the use of PLA reduces the need for non-renewable resources.

PLA has good transparency and smoothness, making it attractive for applications such as packaging materials or adhesive tapes. PLA can be formed by various processing methods such as injection molding, blow molding or extrusion. It combines well with other materials and can be printed on. PLA has a relatively low melting point compared to some other plastics. This makes PLA materials easier to process and 3D print.

In an exemplary embodiment of the invention, the further layer has a proportion of at least 5 wt.% polybutylene adipate terephthalate (PBAT).

Polybutylene adipate terephthalate (PBAT) is a thermoplastic polymer that belongs to the polyester family. PBAT exhibits good mechanical strength, which means it has high tensile strength and stiffness. This allows PBAT to be used in structural applications such as adhesive tapes where strength and resilience are required. PBAT is resistant to many chemicals, including oils, greases, acids and bases. It is less susceptible to corrosion and chemical attack compared to some other plastics. PBAT is a good insulator of electrical current, has good heat resistance and can be used at relatively high temperatures without affecting its properties. It has a comparatively low melting point and is therefore easily processed. PBAT retains its shape and dimensions well under various temperatures and humidity conditions. It has low water absorption, resulting in low shrinkage and deformation. PBAT can be easily colored with dyes, allowing a wide range of color options.

For example, the further layer has a proportion of a mixture of PBAT and PLA. In one embodiment of the invention, the proportion of the mixture is more than 10% by weight, preferably more than 20% by weight, in particular more than 30% by weight and/or less than 60% by weight, preferably less than 50% by weight, in particular less than 40% by weight.

In an exemplary variant of the invention, the mixture for the further layer consists of 30% PBAT and 70% PLA.

In one embodiment of the invention, the mixture for the further layer consists of the compound Bio-Flex ^® S 7710, whereby the proportion of the mixture in the further layer is 30% by weight. Bio-Flex ^® S 7710 is a certified industrially compostable plastic compound that is suitable for the production of production of flat films and subsequent thermoforming, as well as for the production of extruded profiles.

The mixture of PBAT and PLA in the next layer gives the plastic film an advantageous anti-blocking effect. This means that the plastic film can be stored temporarily as a roll until it is processed into an adhesive tape and/or a covering film, for example.

The anti-blocking effect of plastic films refers to the ability to prevent plastic films from sticking or blocking. Plastic films based on ethylene vinyl acetate (EVA) have a tendency to stick to each other due to their sticky surface. This can lead to difficulties in handling, processing and use.

The anti-blocking effect offers several advantages, such as easier handling of the films, the avoidance of blockages during processing and improved stackability of the films. It also reduces the risk of damage or deformation of the films when removing or opening packages.

In addition, the further layer can have a proportion of at least 50 wt.%, preferably at least 60 wt.%, in particular at least 70 wt.% of ethylene vinyl acetate (EVA).

For example, the proportion of vinyl acetate (VA) in the ethylene vinyl acetate (EVA) of the further layer is more than 15 wt.%, preferably more than 25 wt.% and/or less than 50 wt.%, preferably less than 40 wt.%.

The measurement of the thickness of the additional layer was determined according to DIN 53370 and given as an average value. The additional layer has a thickness of more than 3 µm, preferably more than 4 µm, in particular more than 5 µm and/or less than 20 µm, preferably less than 18 µm, in particular less than 16 µm.

For example, the additional layer has a thickness of 14 µm.

In one embodiment of the invention, the at least one layer has a thickness of more than 40 µm, preferably more than 50 µm, in particular more than 60 µm.

Particularly preferred is an embodiment of the adhesive tape according to the invention in which the plastic film is designed to be waterproof for rainwater.

For example, the plastic film comprises a structural layer and/or a pressure-sensitive adhesive coating arranged thereon.

To limit stretching, a grid can be incorporated as a structural layer between the pressure-sensitive adhesive coating and the plastic film or within the pressure-sensitive adhesive coating. At the same time, such a thread structure supports the tearability of the tape in tearable versions.

For example, the plastic film, for example in the form of an adhesive tape, comprises a net-like surface structure made up of a large number of threads or ribbons crossing one another. By providing a carrier layer made up of a net-like surface structure made up of a large number of threads or ribbons crossing one another, a transfer system for the adhesive is provided that ensures that the adhesive is applied extremely evenly. The net-like surface structure can be designed as a net or a fabric, for example. The individual threads or ribbons can also be fused or glued together.

For the design as an adhesive tape or as an adhesive masking film, acrylate-based pressure-sensitive adhesives are preferred due to their good resistance to aging. These acrylate adhesives can generally be applied either as a dispersion or as hot melt adhesives that can be crosslinked using UV radiation. It is also possible to use solvent acrylates or acrylate monomer mixtures or acrylate prepolymers that are polymerized either thermally or using UV radiation after coating. In addition, the use of other pressure-sensitive adhesive classes is also possible, such as adhesives based on synthetic rubber such as SIS (styrene-isoprene-styrene copolymer) or SBS (styrene-butadiene rubber) or silicone or polyurethane-based adhesives.

Paper or foils that are siliconized on one or both sides can be used as a cover for the plastic film as an adhesive tape, for example, and can preferably also be coated with polyethylene (PE) on one or both sides. The films are usually made of PE, PP or corresponding coextrudates. The adhesive is usually coated onto this cover, then dried, cross-linked or polymerized and only then applied to the plastic film in a laminating process.

The plastic film in the form of an adhesive tape can have a width in the range of 30 mm to 1000 mm, preferably in the range from 35 mm to 600 mm, more preferably in the range from 40 mm to 400 mm and particularly preferably in the range from 50 mm to 150 mm. This ensures optimal processability under all occurring conditions.

According to the invention, a method for producing a plastic film is carried out with the steps of extruding at least one layer of a plastic film, connecting to a structural layer, applying a pressure-sensitive adhesive coating. The method for producing a plastic film is carried out to ensure a water vapor diffusion-equivalent air layer thickness (sd value) of less than 15 m, wherein the at least one layer is formed essentially from ethylene vinyl acetate (EVA).

According to the invention, a plastic film is used in an adhesive tape for bonding films in house construction, outdoors, preferably in the area of roofs and facades and/or in a diffusion-open covering film and/or in a self-adhesive covering film for the automotive sector.

The plastic film is extremely robust and has advantageous properties as a film with a membrane for applications in construction or as an effective self-adhesive protective film for high-quality products in the field of mechanical engineering.

For example, the plastic film can be used as a diffusion-open covering film for floors, for example in the application as a painter's covering fleece.

Furthermore, the plastic film can be used as a self-adhesive and diffusion-open covering film for products in the automotive industry, for example as a protective cover for transport.

Further advantages and features of the invention will become apparent from the description of an embodiment with reference to a drawing and from the drawing itself.

• 1 eine schematische Darstellung der erfindungsgemäßen Kunststofffolie in der Ausführung als Klebeband.

This shows

• 1 a schematic representation of the plastic film according to the invention in the form of an adhesive tape.

In 1 is a schematic representation of the embodiment as an adhesive tape, which is formed from the plastic film 1, the structural layer 4 and the pressure-sensitive adhesive coating 5. The structural layer 4 is arranged between the plastic film 1 and the pressure-sensitive adhesive coating 5 in the embodiment variant shown.

In the embodiment shown, the plastic film 1 is designed in three layers, consisting of the centrally arranged at least one layer 2 and the further layers 3 surrounding at least one layer 2.

The plastic film 1 has a thickness of 80 µm, the at least one layer 2 has a thickness of 52 µm and the other layers 3 each have a thickness of 14 µm.

In the illustrated embodiment, the plastic film 1 has a stress of 4 MPa according to DIN EN ISO 527-3 at 5% elongation, whereby the s _d value of the plastic film 1 is 1.2 m.

The at least one layer 2 consists almost entirely of ethylene vinyl acetate (EVA), with the proportion of vinyl acetate (VA) being 28% by weight, whereby a favorable water vapor permeability can be achieved.

The further layer 3 comprises a 30 wt.% mixture of 30% PBAT and 70% PLA. In the embodiment shown, the mixture for the further layer 3 consists of the compound Bio-Flex ^® S 7710, which gives the plastic film 1 an advantageous anti-blocking effect.

The further layer 3 has a proportion of 70 wt.% ethylene vinyl acetate (EVA), with the proportion of vinyl acetate (VA) being 28 wt.%.

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• EP 1 847 577 B1 [0004]
• DE 20 2010 014 075 U1 [0005]

Claims (15)

Plastic film (1) with at least one layer (2, 3), characterized in that the at least one layer (2) consists essentially of ethylene-vinyl acetate (EVA), wherein the ethylene-vinyl acetate (EVA) has a proportion of vinyl acetate (VA) of at least 15% by weight, to ensure a water vapor diffusion equivalent air layer thickness (s _d value) of less than 15 m and at least one layer (2, 3) has a proportion of at least 5% by weight of polylactide (PLA). plastic film after claim 1 , characterized in that at least one layer (2, 3) has a proportion of at least 5 wt.% polybutylene adipate terephthalate (PBAT). plastic film after claim 1 or 2 , characterized in that the s _d value is less than 8 m, preferably less than 5 m, in particular less than 2 m. Plastic film according to one of the Claims 1 until 3 , characterized in that the proportion of ethylene vinyl acetate (EVA) in the at least one layer is more than 90 wt.%, preferably more than 95 wt.%, in particular more than 97.5 wt.%. Plastic film according to one of the Claims 1 until 4 , characterized in that the proportion of vinyl acetate (VA) in the ethylene vinyl acetate (EVA) is more than 20 wt.%, preferably more than 25 wt.% and/or less than 50 wt.%, preferably less than 40 wt.%. Plastic film according to one of the Claims 1 until 5 , characterized in that the plastic film (1) has a thickness of more than 20 µm, preferably more than 40 µm, in particular more than 60 µm and/or less than 120 µm, preferably less than 105 µm, in particular less than 90 µm. Plastic film according to one of the Claims 1 until 6 , characterized in that the plastic film (1) has a stress of more than 2 MPa, preferably more than 3 MPa, in particular more than 4 MPa according to DIN EN ISO 527-3 at 5% elongation. Plastic film according to one of the Claims 1 until 7 , characterized in that the plastic film (1) comprises at least one further layer (3). plastic film after claim 8 , characterized in that the at least one layer (2) is surrounded by a further layer (3). plastic film after claim 8 or 9 , characterized in that the further layer (3) has a proportion of at least 50 wt. %, preferably of at least 60 wt. %, in particular of at least 70 wt. % of ethylene vinyl acetate (EVA), wherein the proportion of vinyl acetate (VA) is more than 15 wt. %, preferably more than 25 wt. %, and/or less than 50 wt. %, preferably less than 40 wt. %. Plastic film according to one of the Claims 8 until 10 , characterized in that the further layer (3) has a thickness of more than 3 µm, preferably more than 4 µm, in particular more than 5 µm and/or less than 20 µm, preferably less than 18 µm, in particular less than 16 µm. Plastic film according to one of the Claims 1 until 11 , characterized in that the at least one layer (2) has a thickness of more than 40 µm, preferably more than 50 µm, in particular more than 60 µm. Plastic film according to one of the Claims 1 until 12 , characterized in that the plastic film (1) comprises a structural layer (4) and/or a pressure-sensitive adhesive coating (5) arranged thereon. Method for producing a plastic film with the following steps: - extrusion of at least one layer (2) of a plastic film (1), - bonding to a structural layer (4), - applying a pressure-sensitive adhesive coating (5), characterized in that in order to ensure a water vapor diffusion-equivalent air layer thickness (s _d value) of less than 15 m, the at least one layer (2) is formed essentially from ethylene vinyl acetate (EVA). Use of a plastic film according to one of the Claims 1 until 13 in an adhesive tape for bonding films in house construction, outdoors, preferably in the area of roofs and facades and/or in a diffusion-open covering film and/or in a self-adhesive covering film for the automotive sector.

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