Film having increased water vapor permeability

Abstract

The invention relates to a plastic film (10) composed of at least one layer (2, 3). The at least one layer (2) is essentially composed of ethylene vinyl acetate (EVA), the ethylene vinyl acetate (EVA) having a proportion of vinyl acetate (VA) of at least 15 wt.%, to ensure a water vapor diffusion-equivalent air layer thickness (sd value) of less than 15 m. The at least one layer (2, 3) has a proportion of at least 5 wt.% of a functional thermoplastic.

Description

[0001] Film with increased water vapor permeability

[0002] Description

[0003] The invention relates to a plastic film comprising at least one layer.

[0004] In the construction sector, very diffusion-open materials are generally preferred for the external insulation of buildings in order to dissipate penetrated moisture and / or residual moisture in the building materials to the outside.

[0005] In general, single-sided adhesive tapes are used for bonding films in house construction according to the state of the art, which in particular comprise films based on polyethylene, PVC or thermally compacted spunbonded carriers.

[0006] 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 vapor-permeable bonding of roofing membranes above the insulation layer. In addition to a low Sd value of approximately 12 m, a special elongation behavior is highlighted as important. A characteristic parameter for this is the difference between the percentage total elongation under load and the percentage residual elongation after loading.

[0007] DE 20 2010 014 075 U1 discloses a technical adhesive tape, 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 at least on one side, which has a basis weight of at least 100 g / m 2The carrier comprises a cast polyolefin film that is so elastic and plastically extensible that the difference between the percentage total elongation under load and the percentage permanent elongation after subsequent release of load is in the range of 15 to 50%. Thus, adhesive tapes with elastic behavior already exist, but they usually do not offer sufficient rigidity to permanently and reliably bond films under tension.

[0008] The object of the present invention is to provide a plastic film that offers good sealing properties while simultaneously offering good water vapor permeability. The plastic film should be suitable for securing construction films, particularly films used in the building envelope. Furthermore, the plastic film should be able to exhibit sufficiently high tension and good rigidity when bonded.

[0009] 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 dependent claims, the description, the exemplary embodiment, and the drawing.

[0010] 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 wt.% to ensure a water vapor diffusion equivalent air layer thickness (Sd value) of less than 15 μm and at least one layer has a proportion of at least 5 wt.% of a functional thermoplastic.

[0011] The Sd value is important in building physics, especially in the design of buildings and the selection of building materials. It influences moisture regulation in a building and can impact the indoor climate and energy efficiency. For example, an excessively high or insufficient vapor barrier can lead to moisture problems such as mold growth. The Sd 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 impedes the passage of water vapor. The Sd value is expressed in meters.

[0012] A low Sd value means that a material is vapor-permeable and allows water vapor to pass through relatively easily. A high Sd value, on the other hand, indicates that a material is vapor-tight and significantly impedes or even prevents the passage of water vapor.

[0013] DIN 52615 is a German standard entitled "Determination of the water vapor diffusion resistance and moisture content of building materials - Climate chamber method." This standard specifies a method for determining the water vapor diffusion resistance (Sd value) and moisture content of building materials.

[0014] The climate chamber method, described in DIN 52615, enables the measurement of a building material's water vapor diffusion resistance by exposing it to a defined humidity and temperature in a climate chamber. By measuring the moisture content of the building material before and after exposure, the water vapor diffusion resistance can be calculated.

[0015] For example, the Sd value of the plastic film is less than 8 m, preferably less than 5 m, in particular less than 2 m and is therefore ideally suited to ensure the required water vapor permeability.

[0016] In an advantageous embodiment of the invention, the Sd value of the plastic film is less than 1.2 m. Alternatively to the Sd 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 sample of 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) be detected. The detection limit also depends on the sample properties and the sample thickness.

[0017] For example, the plastic film has a water vapor transmission rate of more than 20 g / (m 2 ■ d), preferably more than 25 g / (m 2 ■ d), in particular of more than 30 g / (m 2■ d) according to DIN 53116 and is therefore ideally suited as a plastic film for adhesive tapes.

[0018] The advantageous water vapor permeability is achieved, for example, through the use of 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 wt.%, preferably more than 95 wt.%, in particular more than 97.5 wt.%.

[0019] Ethylene-vinyl acetate (EVA) is a copolymer made from the monomers ethylene, vinyl acetate, and optionally other comonomers. It is a thermoplastic material with a wide range of applications.

[0020] 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), particularly its water vapor permeability and adhesiveness, can be precisely adjusted by varying the proportion of vinyl acetate monomer. Ethylene-vinyl acetate (EVA) is also particularly distinguished by its good weather resistance, electrical insulation properties, and transparency to certain wavelengths of light.

[0021] 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.

[0022] The proportion of vinyl acetate (VA) of the ethylene vinyl acetate (EVA) is, for example, more than 20 wt.%, preferably more than 25 wt.% and / or less than 50 wt.%, preferably less than 40 wt.%, in order to achieve favorable water vapor permeability.

[0023] 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). Copolymerization of vinyl acetate with ethylene produces EVA, a flexible and water vapor-permeable material.

[0024] 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 provides a good feel and a stable band for robust applications.

[0025] At the same time, the plastic film has a desirable tension in addition to the advantageous water vapor permeability.

[0026] Films and sheets up to 1 mm thick are tested using strip or shoulder specimens. According to ISO 527-3 and ASTM D 882, strips are the usual specimen shape. This specimen shape can be easily produced using a cutting press or a film cutter. Shoulder specimens are often used in quality control. In this case, a direct-measuring extensometer is required, which can record the specimen strains directly on the specimen. Typical test results include yield stress, yield strain, maximum stress, and nominal strain at break.

[0027] 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 AL of the measuring section Lo.

[0028] 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, allowing the necessary stress to be achieved as a plastic film, for example, in the form of an adhesive tape.

[0029] For example, the plastic film is designed as a monolayer film and has a rather small thickness.

[0030] The at least one layer of the monofilm contains, for example, a proportion of at least 5 wt.% of a functional thermoplastic.

[0031] In one variant of the invention, the functional thermoplastic is embodied as a polylactide (PLA). PLA reduces the stickiness of the film, which is advantageous for processing and application.

[0032] In one variant, the plastic film contains more than 10 wt.%, preferably more than 15 wt.%, in particular more than 20 wt.% polylactide (PLA). This monofilm is very thin yet offers increased rigidity. The PLA content greatly increases rigidity, making it possible to dispense with a structural layer, for example.

[0033] In an exemplary embodiment of the invention, the at least one layer has a proportion of at least 5 wt.% polybutylene adipate terephthalate (PBAT).

[0034] In a further variant of the invention, the functional thermoplastic is embodied as polystyrene (PS). For example, the polystyrene is embodied as GPPS (General Purpose Polystyrene). The PS advantageously reduces the stickiness of the film during processing and application and grants the film exceptional tearability exclusively in the transverse direction, which is advantageous for the film's use as an adhesive tape.

[0035] In an alternative variant of the invention, the functional thermoplastic is designed as a mixture of a PS and a PLA.

[0036] Polystyrene is a synthetic polymer made from the monomer styrene. Polystyrene is transparent, particularly hard, and lends the film advantageous rigidity.

[0037] The Melt Flow Index (MFI) is a measurement that indicates the flowability of thermoplastics under standardized conditions. Specifically, the MFI is measured as the mass of plastic material in grams that flows through a standardized nozzle at a specific temperature and load within a specified time. The unit is g / 10 min. The MFI is an important measure of the processability of plastics in various applications, as it provides information about the material's flow properties. The higher the MFI value, the better the plastic flows, and vice versa. Polystyrene, for example, has an MFI (at 200 °C and 5 kg) of more than 8 cm 3 / 10 min and less than 16 cm 3 / 10 min, which favors the blow extrusion of the film.

[0038] In a variant of the invention, the polystyrene has an MFI (at 200 °C and at 5 kg) of more than 10 cm 3 / 10 min and less than 14 cm 3 / 10 min.

[0039] For example, polystyrene has a density of more than 1.01 g / cm 3 and less than 1.07 g / cm 3 on.

[0040] In a variant of the invention, the polystyrene has a density of more than 1.03 g / cm 3 and less than 1.05 g / cm 3 on.

[0041] 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.

[0042] The desired rigidity can be achieved, for example, by combining the at least one layer with another layer. For this purpose, the plastic film comprises at least one additional layer.

[0043] For example, at least one layer is surrounded by another layer, thus forming the plastic film in a sandwich configuration. As a three-layer film with a thick central layer and a thin outer layer, the plastic film exhibits particularly good properties with regard to Sd value, water vapor permeability, and tension.

[0044] In an exemplary embodiment of the invention, the additional layer contains at least 5 wt.% polylactide (PLA). Polylactide (PLA) stands for polylactic acid. Polylactide is biodegradable, meaning it can be broken down by microorganisms or enzymes into natural compounds such as carbon dioxide and water. This enables more environmentally friendly disposal compared to conventional plastics. Polylactide is obtained from plant sources such as corn starch, sugar cane, or other sugar plants. Compared to petroleum-based plastics, the use of PLA reduces the need for non-renewable resources.

[0045] PLA exhibits good transparency and smoothness, making it attractive for applications such as packaging materials or adhesive tapes. PLA can be molded using various processing methods such as injection molding, blow molding, or extrusion. It combines well with other materials and can be printed. PLA has a relatively low melting point compared to some other plastics. This makes it easier to process and 3D print PLA materials.

[0046] In an exemplary embodiment of the invention, the further layer has a proportion of at least 5 wt.% polybutylene adipate terephthalate (PBAT).

[0047] Polybutylene adipate terephthalate (PBAT) is a thermoplastic polymer belonging to the polyester family. PBAT exhibits good mechanical strength, meaning it has high tensile strength and stiffness. This allows it 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 than some other plastics. PBAT is a good electrical insulator, has good heat resistance, and can be used at relatively high temperatures without compromising 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 for a wide range of color options.

[0048] For example, the additional layer comprises a mixture of PBAT and PLA. In one embodiment of the invention, the proportion of the mixture is more than 10 wt.%, preferably more than 20 wt.%, in particular more than 30 wt.% and / or less than 60 wt.%, preferably less than 50 wt.%, in particular less than 40 wt.%.

[0049] In an exemplary variant of the invention, the mixture for the further layer consists of 30% PBAT and 70% PLA.

[0050] In one embodiment of the invention, the mixture for the additional layer consists of the compound Bio-Flex® S 7710, with the proportion of the mixture in the additional layer being 30% by weight. Bio-Flex® S 7710 is a certified industrially compostable plastic compound suitable for the production of flat films and subsequent thermoforming, as well as for the production of extruded profiles.

[0051] The blend of PBAT and PLA in the next layer provides the plastic film with a beneficial anti-blocking effect. This allows the plastic film to be stored temporarily in roll form until it is processed, for example, into adhesive tape and / or masking film.

[0052] In an alternative variant of the invention, the additional layer contains a proportion of polystyrene. In one embodiment of the invention, the proportion of polystyrene is more than 5 wt.%, preferably more than 10 wt.%, in particular more than 15 wt.% and / or less than 50 wt.%, preferably less than 40 wt.%, in particular less than 25 wt.%. The polystyrene in the additional layer also achieves an advantageous anti-blocking effect of the plastic film.

[0053] Antiblocking properties in plastic films refer to the ability to prevent sticking or blocking of plastic films. Ethylene vinyl acetate (EVA)-based plastic films tend to stick to each other due to their sticky surface. This can lead to difficulties in handling, processing, and use.

[0054] The anti-blocking effect offers several advantages, such as easier handling of the films, the prevention 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.

[0055] In addition, the further layer may contain at least 50% by weight, preferably at least 60% by weight, in particular at least 70% by weight of ethylene vinyl acetate (EVA).

[0056] 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.%.

[0057] The thickness of the additional layer was measured according to DIN 53370 and reported as an average value. The additional layer has a thickness of more than 3 pm, preferably more than 4 pm, in particular more than 5 pm, and / or less than 20 pm, preferably less than 18 pm, in particular less than 16 pm. For example, the additional layer has a thickness of 14 pm.

[0058] In one embodiment of the invention, the at least one layer has a thickness of more than 40 pm, preferably more than 50 pm, in particular more than 60 pm.

[0059] 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.

[0060] For example, the plastic film comprises a structural layer and / or a pressure-sensitive adhesive coating arranged thereon.

[0061] To limit stretching, a scrim can be incorporated as a structural layer between the adhesive coating and the plastic film, or within the adhesive coating. At the same time, such a scrim supports the tearability of the tape in tearable versions.

[0062] For example, in the form of an adhesive tape, the plastic film comprises a net-like structure made up of a multitude of intersecting threads or ribbons. Providing a carrier layer made up of a net-like structure made up of a multitude of intersecting threads or ribbons provides a transfer system for the adhesive that ensures extremely even application of the adhesive. The net-like structure can be designed as a net or a woven fabric, for example. The individual threads or ribbons can also be fused or glued together.

[0063] For adhesive tape or adhesive masking film applications, acrylate-based pressure-sensitive adhesives are preferred due to their good aging resistance. These acrylate adhesives can generally be applied either as a dispersion or as hot melt adhesives that are crosslinked using UV radiation. Solvent-based acrylates, acrylate monomer mixtures, or acrylate prepolymers, which are polymerized either thermally or using UV radiation after coating, are also possible. Furthermore, 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.

[0064] For example, paper or foils siliconized on one or both sides can be used as a backing for the plastic film used as an adhesive tape. These foils can also be coated with polyethylene (PE) on one or both sides. These foils are typically made of PE, PP, or corresponding coextrudates. The adhesive is typically coated onto this backing, then dried, crosslinked, or polymerized, and only then applied to the plastic film in a lamination process.

[0065] 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 of 35 mm to 600 mm, more preferably in the range of 40 mm to 400 mm, and particularly preferably in the range of 50 mm to 150 mm. This ensures optimal processability under all conditions.

[0066] According to the invention, a method for producing a plastic film is carried out, comprising the steps of extruding at least one layer of a plastic film, bonding it to a structural layer, and 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 μm, 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 cover film and / or in a self-adhesive cover film for the automotive sector.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] This shows

[0072] Fig. 1 is a schematic representation of the plastic film according to the invention in the form of an adhesive tape.

[0073] Fig. 1 shows a schematic representation of the adhesive tape embodiment, which is formed from the plastic film 1, the structural layer 4, and the pressure-sensitive adhesive coating 5. In the illustrated embodiment, the structural layer 4 is arranged between the plastic film 1 and the pressure-sensitive adhesive coating 5.

[0074] 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.

[0075] The plastic film 1 has a thickness of 80 pm, the at least one layer 2 has a thickness of 52 pm and the further layers 3 each have a thickness of 14 pm.

[0076] 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 Sd value of the plastic film 1 is 1.2 m.

[0077] 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.

[0078] The additional layer 3 comprises a 30 wt. % mixture of 30% PBAT and 70% PLA. In the illustrated embodiment, the mixture for the additional layer 3 consists of the compound Bio-Flex® S 7710, which gives the plastic film 1 a beneficial anti-blocking effect.

[0079] The further layer 3 has a proportion of 70 wt.% ethylene vinyl acetate (EVA), with the proportion of vinyl acetate (VA) being 28 wt.%.

[0080] The plastic film 1 in the embodiment in a further three-layer design variant has a comparable thickness and the identical Sd value as the plastic film in the figure description and is formed from the following materials:

Claims

Patent claims 1 . 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 wt.%, to ensure a water vapor diffusion equivalent air layer thickness (Sd value) of less than 15 μm and at least one layer (2, 3) has a proportion of at least 5 wt.% of a functional thermoplastic.

2. Plastic film according to claim 1, characterized in that the functional thermoplastic is made of a polylactide (PLA).

3. Plastic film according to claim 1 or 2, characterized in that the functional thermoplastic is made of a polystyrene (PS).

4. Plastic film according to one of claims 1 to 3, characterized in that at least one layer (2, 3) has a proportion of at least 5 wt.% polybutylene adipate terephthalate (PBAT).

5. Plastic film according to claim 3 or 4, characterized in that the polystyrene (PS) has a density of more than 1.01 g / cm 3 and less than 1.07 g / cm 3 has.

6. Plastic film according to one of claims 3 to 5, characterized in that the polystyrene has an MFI at 200 °C and at 5 kg according to ISO 1133 of more than 8 cm 3 / 10 min and less than 16 cm 3 / 10 min.

7. Plastic film according to one of claims 1 to 6, characterized in that the Sd value is less than 8 m, preferably less than 5 m, in particular less than 2 m.

8. Plastic film according to one of claims 1 to 7, 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.%.

9. Plastic film according to one of claims 1 to 8, 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.%.

10. Plastic film according to one of claims 1 to 9, characterized in that the plastic film (1) has a thickness of more than 20 pm, preferably more than 40 pm, in particular more than 60 pm and / or less than 120 pm, preferably less than 105 pm, in particular less than 90 pm.

11. Plastic film according to one of claims 1 to 10, 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.

12. Plastic film according to one of claims 1 to 11, characterized in that the plastic film (1) comprises at least one further layer (3).

13. Plastic film according to claim 12, characterized in that the at least one layer (2) is surrounded by a further layer (3).

14. Plastic film according to claim 12 or 13, 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.% 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.%.

15. Plastic film according to one of claims 11 to 14, characterized in that the further layer (3) has a thickness of more than 3 pm, preferably more than 4 pm, in particular more than 5 pm and / or less than 20 pm, preferably less than 18 pm, in particular less than 16 pm.

16. Plastic film according to one of claims 1 to 15, characterized in that the at least one layer (2) has a thickness of more than 40 pm, preferably more than 50 pm, in particular more than 60 pm.

17. Plastic film according to one of claims 1 to 16, characterized in that the plastic film (1) comprises a structural layer (4) and / or a pressure-sensitive adhesive coating (5) arranged thereon.

18. A method for producing a plastic film comprising the following steps: extrusion of at least one layer (2) of a plastic film (1), bonding to a structural layer (4), Application of a pressure-sensitive adhesive coating (5), characterized in that, in order to ensure a water vapor diffusion-equivalent air layer thickness (Sd value) of less than 15 m, the at least one layer (2) is formed essentially from ethylene-vinyl acetate (EVA).

19. Use of a plastic film according to one of claims 1 to 17 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 cover film and / or in a self-adhesive Covering film for the automotive sector.

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