Flame-retardant breathable film

Abstract

Disclosed is a flame retardant film comprising: a base sheet comprising glass fibers, the base sheet having a basis weight of 296 to 420 g / m2 and a maximum organic content of 1.5 weight percent; and a thermoplastic elastomer film attached to the base sheet, the film having a basis weight of 20 to 35 grams per square meter; wherein the thermoplastic elastomer film is attached to the base sheet by using an adhesive present discontinuously between the film and the sheet in an areal density of 25% to 40% and an amount of 4 to 6 grams per square meter; and wherein the flame retardant film has a total heat of combustion (PCS) of less than 3 MJ / kg and less than 4 MJ / sqm as measured according to EN ISO 1716.

Description

Background Technology

[0001] Technical Field This invention relates to sheet structures suitable for use in buildings and constructions, specifically flame-retardant sheet structures that prevent the passage of liquid water but allow the passage of water vapor; and these sheet structures are suitable for use as facade products on buildings. Sheet structures are particularly suitable for use in buildings with open facades employing spacers, wherein the sheet structure can be exposed to the environment.

[0002] Explanation of relevant technologies. Recent high-profile building fires, such as the Grenfell Tower fire in West London, have brought attention to improved fire-retardant building cladding materials. When a fire starts on a lower floor, it spreads rapidly upwards along the building's exterior to all residential floors, accelerated by the hazardous flammable cladding and external insulation, and the air gaps that create a chimney effect between them.

[0003] This type of construction may include an exterior cladding installed on the building's sheathing material, and in some cases, the installation includes spacers that install the cladding to create an air gap between the cladding and the building's sheathing material. In some cases, a breathable but waterproof layer between the cladding and the sheathing material is desired to provide improved energy efficiency to the building. Typically, this breathable but waterproof layer is installed on the surface of the sheathing material and is referred to as a "breather membrane" or a waterproof barrier layer (WRB).

[0004] The development of fully non-combustible and breathable membranes with high permanent waterproofing and water vapor permeability remains challenging. Currently, sheet structures used as breathable membranes in these types of facade applications have significant negative properties.

[0005] One such sheet structure is a heavy three-layer structure: glass fiber with a microporous polymer layer on the surface and a perforated aluminum outer surface; the aluminum is perforated to achieve the desired breathability of the sheet structure. This sheet structure can meet many breathability and water resistance requirements, and even the European A2 fire resistance rating. However, the use of a microporous membrane is undesirable because water resistance can be affected by surfactants, which may reduce the surface contact angle, allowing water to permeate through the micropores; this means that water resistance is not permanent. Furthermore, the manufacture of this sheet structure requires combining, assembling, and attaching three different types of layers together; the associated complexity and cost are undesirable.

[0006] Therefore, a two-layer sheet structure would be simpler and more desirable, and one such sheet structure is a glass fiber layer with a continuously coated surface of extruded silicone, polyurethane, or acrylic polymers. However, this material has low permeability or limited ability to prevent water intrusion. Intuitively, the ability to reduce water intrusion can be improved by providing a thicker coating; however, this, in turn, will further reduce permeability or water vapor transport, or compromise fire resistance due to the increased PCS value.

[0007] Therefore, there is increasing pressure within the industry for higher fire resistance requirements, and stricter regulations are expected; there is a need for non-combustible, breathable, and watertight membranes for facade applications. A particular need is for a breathable membrane with a two-layer structure and a desired combination of vapor permeability, liquid water resistance, and non-combustibility. Specifically, there is a need for a breathable membrane that meets the so-called "trinity" characteristics at a high-performance level, which is a combination of sufficient breathability (Sd value < 0.12 meters); water resistance (W1 rating); and non-combustibility (fire resistance rating A2). Summary of the Invention

[0008] This invention relates to a flame-retardant film comprising: a base sheet comprising glass fibers having a basis weight of 296 to 420 g / m² and a maximum organic content of 1.5% by weight; and a thermoplastic elastomer film attached to the base sheet having a basis weight of 20 to 35 g / m²; wherein the thermoplastic elastomer film is attached to the base sheet by means of an adhesive, the adhesive being present discontinuously between the film and the sheet at an areal density of 25% to 40% and in an amount of 4 to 6 g / m²; and wherein the flame-retardant film has a total heat of combustion (PCS) of less than 3 MJ / kg and less than 4 MJ / sqm as measured according to EN ISO 1716. Detailed Implementation

[0009] The present invention relates to a flame-retardant and breathable membrane, which is a two-layer structure with desired three-in-one properties; the breathable membrane can be combined with flame-retardant strips to provide a lightweight and non-combustible protective layer on the interior or exterior facade of a building.

[0010] Calorific value is the amount of energy produced by the complete combustion of a material. This amount of energy determines how much heat a material contributes to a fire. Simply put, more heat means a fire spreads faster. The calorific value of a panel is expressed by its PCS (an abbreviation of the French term 'Pouvoir Calorifique Supérieur' [higher heating value]). The higher the PCS value, the more calorific value the panel has; that is, the greater its contribution to the fire.

[0011] In the European Union, EN13501-1 provides fire rating classifications (known as the European rating system), with rating names ranging from the most stringent ratings A1 and A2 to ratings B, C, D, E, and F. These ratings reflect a progression in non-combustibility, with ratings A1 and A2 being non-combustible and ratings B through F being combustible. When you use non-combustible materials, you essentially eliminate fire risk in your design because the material does not contribute significantly to fire resistance. The non-combustibility ratings for A1 and A2 reflect set limits on the material's calorific value (PCS value). For combustible materials (BF), these limits are not set. Non-combustible facade materials (European ratings A1 and A2) have very low calorific values ​​and therefore contribute very little to fire resistance, with European rating A1 having a lower PCS limit than European rating A2.

[0012] The breathable membrane comprises a base sheet containing glass fiber and a thermoplastic elastomer film attached to the base sheet with an adhesive. Specifically, the breathable membrane is a combination of a glass fiber fabric with a very low organic content and a very thin monolithic thermoplastic polyurethane (TPU) film layer, assembled together with a small amount of polyurethane adhesive that does not sacrifice vapor permeability for water resistance. The breathable membrane meets the requirements of the European A2 fire rating.

[0013] The base sheet containing glass fiber is preferably a plain-weave glass fabric, and in some embodiments, the base sheet contains E-glass. In some embodiments, the base sheet is an E / ECR (corrosion-resistant E-glass) glass mat with a plain weave using leno weft. It is believed that base sheets containing ceramic or silica glass can be used, provided that they meet the organic content requirements.

[0014] The base sheet has a basis weight of 296 to 420 g / m², and in some embodiments has a basis weight of 360 to 385 g / m². In some embodiments, the base sheet has a basis weight of 360 to 370 g / m².

[0015] The base sheet has a maximum organic content of 1.5% by weight, which is based solely on the weight of the base sheet. In some preferred embodiments, the base sheet has a maximum organic content of 1.0% by weight, which is also based solely on the weight of the base sheet (i.e., the total weight of the organic material plus the glass). In some embodiments, the base sheet has a total heat of combustion (PCS) of less than 0.38 MJ / kg as measured according to EN ISO 1716. In some other embodiments, the base sheet has a total heat of combustion (PCS) of less than 0.25 MJ / kg as measured according to EN ISO 1716. It is believed that a base sheet with a low organic content can be made by controlling the amount of organic materials used (such as the amount of binders and / or fiber finishing agents) during the manufacture of the base sheet, or by washing or removing organic matter from the base sheet after manufacture through chemical or thermal treatment, or some combination of both techniques.

[0016] The flame-retardant film comprises a thermoplastic elastomer film layer attached to a base sheet. The thermoplastic elastomer film layer provides the sheet with the desired water resistance while also providing sufficient water vapor permeability. Specifically, the film is preferably a monolithic film layer, and the thermoplastic elastomer is a hydrophilic material. Therefore, a monolithic thermoplastic elastomer film layer is hydrophilic, meaning it can transfer a significant amount of water vapor through the film by absorbing water on the side with a higher water concentration and desorbing or evaporating water on the other side with a lower water concentration. Hydrophilicity is defined as having a contact angle ranging from 0 to 90 degrees, as determined by ASTM D5946-17. "Monolithic" means that the film is not a microporous film and does not have continuous pores throughout its thickness. Thermoplastic elastomers are specified as six general categories by ISO 18064:2022. Three of these categories can be sufficiently hydrophilic to act as a water vapor permeable layer. These categories are thermoplastic polyurethane (TPU), thermoplastic copolyester (TPE-E), and thermoplastic polyamide (TPE-A).

[0017] The thermoplastic elastomer film attached to the base sheet has a basis weight of 20 to 35 g / m². In some embodiments, the thermoplastic elastomer film has a basis weight of 25 to 31 g / m². In some embodiments, the thermoplastic elastomer film has a thickness of 18 to 31 micrometers. In some preferred embodiments, the thermoplastic elastomer film has a thickness of 22 to 28 micrometers.

[0018] In some embodiments, the thermoplastic elastomer film may comprise a TPC-E elastomer; the TPC-E elastomer contains hard crystalline polyester blocks and long-chain soft amorphous polyether blocks. Examples of TPC-E materials are products marketed under the Hytrel® brand. In some embodiments, the thermoplastic elastomer film may comprise a TPE-A elastomer. The TPE-A elastomer contains hard polyamide blocks and soft amorphous polyether blocks. Examples of TPE-A materials are products marketed under the PEBAX® and VESTAMID® E brands.

[0019] In some embodiments, the thermoplastic elastomer film is a TPU elastomer. The TPU elastomer comprises an aromatic polyurethane polymer based on linear segment block copolymers, which consist of hard and soft segments, reacted with a polyester or polyether glycol using a diisocyanate. Examples of TPU materials are products marketed under the brand names Platilon®, Pellethane®, and Estane®. A preferred TPU embodiment is Platilon® U.

[0020] It has been found that microporous membranes are less than desirable for providing permanent waterproofing to the base sheet within a breathable membrane. Microporous membranes refer to extruded or cast films or coatings with pores of a size that allow vapor molecules to pass through while blocking liquid water droplets, and whose surface energy may have been modified to reduce their wetting ability. These microporous membranes are less ideal as facade materials because any surfactants used to clean building exteriors can alter the surface energy of the microporous membrane, allowing it to wet and failing to provide the desired level of sustained waterproofing.

[0021] The thermoplastic elastomer film is attached to a base sheet using an adhesive. The adhesive is discontinuous between the base sheet and the film; that is, the adhesive neither continuously covers the surface of the base sheet or the film, nor forms a continuous layer between them. This lack of a continuous adhesive layer allows the breathable membrane to "breathe," thus allowing water vapor to move through the membrane between the individual adhesive joints. Suitable techniques, such as direct gravure printing, can be used to apply the adhesive discontinuously to one or both of the base sheet or film layers, providing separate adhesive domains on the surfaces of the base sheet and / or film. These domains form the joints or adhesive points between the base sheet and the film. The discontinuous adhesive can be applied in any desired pattern, such as lines, dots, polygons, or other shapes. Suitable methods for applying adhesives and attaching sheet materials in discontinuous patterns are described, for example, in U.S. Patent Nos. 5,874,140; 5,531,419; 7,55,377; and U.S. Patent Publication US 20050130521 A1, all of which are attributed to Wyner et al.

[0022] Just as microporous films have been found unsuitable for use in breathable membranes, films directly extruded onto the surface of a base sheet have also been found unsuitable. Such directly extruded films suffer from pinhole problems, which affect water resistance. These pinholes are believed to be due to surface characteristics of the glass fiber-containing base sheet, which may have random glass filaments extending from the sheet, potentially penetrating the necessarily thin extruded film. Therefore, it has been found that discontinuously adhering a monolithic film to the base sheet tends to mitigate any problems associated with the surface roughness of the base sheet, because, unlike directly extruded films, the surface of the monolithic film layer is discontinuously bonded to the surface of the base sheet.

[0023] The adhesive is present discontinuously between the film and the sheet at a areal density of 25% to 40%, and at an amount of 4 to 6 grams per square meter. In some embodiments, the adhesive is present discontinuously between the film and the sheet at a areal density of 30% to 35%. In a preferred embodiment, the adhesive is present discontinuously between the film and the base sheet as uniformly applied adhesive fields or dots. In some embodiments, the adhesive is polyurethane. Alternative adhesives may include epoxy resins and hot melt adhesives.

[0024] In a preferred embodiment, the flame-retardant film consists of two layers. As used herein, the term "layer" refers to a discrete region of material in the form of a film or other sheet material. Therefore, the adhesive array between the layers is not considered a layer herein.

[0025] The two flame-retardant films bonded together have a total heat of combustion (PCS) of less than 3 MJ / kg and less than 4 MJ / sqm as measured according to EN ISO 1716, and preferably have a European Class A2 fire rating according to EN 13501-1.

[0026] In some embodiments, the flame-retardant membrane has an equivalent air layer thickness (Sd value) of less than 0.12 meters for water vapor diffusion, as measured by EN ISO 12572. In some other embodiments, the flame-retardant membrane has an equivalent air layer thickness (Sd value) of less than 0.1 meters for water vapor diffusion, as measured by EN ISO 12572. The Sd value is a measure of the membrane's resistance to moisture diffusion, expressed as an equivalent air layer thickness. The unit of measurement is meters.

[0027] In some embodiments, the flame-retardant membrane showed no signs of water penetration after being exposed to a 200 mm water column for 2 hours, according to EN 1928 (Method A). This is equivalent to a watertightness rating of W1, which, according to the test method, requires zero water leakage at 200 mm.

[0028] In some embodiments, after UV aging at 50°C for at least 5000 hours corresponding to 800 MJ / m² according to EN 1297, the flame-retardant film showed no signs of water penetration after exposure to a 200 mm water column for 2 hours according to EN 1928 (Method A). This is equivalent to a watertightness rating of W1.

[0029] Flame-retardant films can be used as a material layer in facades or wall systems, particularly near or on the exterior of the wall, preferably between the exterior cladding and the wall support structure. Preferably, the material layer of the flame-retardant film is made of segments of individual flame-retardant film layers that cover the wall and further overlap at the edges. This type of arrangement of individual flame-retardant film layers is considered herein to be multiple “layered segments” of the flame-retardant film. Preferably, the edge of the first layered segment of the flame-retardant film overlaps with the edge of the second layered segment of the flame-retardant film by at least 100 mm.

[0030] In some embodiments, the layered sections of the flame-retardant membrane are further sealed with flame-retardant tape, and in some embodiments, the tape has a total heat of combustion (PCS) of less than 7.4 MJ / kg and less than 1.6 MJ / sqm, as measured according to EN ISO 1716. Additionally, in some embodiments, the total surface area coverage of the tape on the facade or wall system is 5.4% or less, based on the area coverage of the material layer including the flame-retardant membrane on the wall structure.

[0031] In some embodiments, the facade or wall system has an outer surface and an inner surface, and the facade or wall system may further include multiple layers of a vapor barrier membrane closer to the inner surface of the wall structure than the layered sections of the flame-retardant membrane. This vapor barrier membrane may also be sealed with tape. In a preferred embodiment, the edge of a first layer of the vapor barrier membrane overlaps with a second layer of the vapor barrier membrane by at least 100 mm. In some embodiments, the vapor barrier membrane has a total heat of combustion (PCS) of less than 0.51 MJ / kg and less than 0.1 MJ / sqm. In some embodiments, the total area surface coverage of the tape on the vapor barrier membrane is 5.4% or less.

[0032] Test methods

[0033] EN ISO 1716:2018 is a heat of combustion test to determine the maximum potential total heat release of a product upon complete combustion, regardless of its end use. This test is also relevant to grades A1 and A2 and their sub-grades. This test is used to determine both total heat of combustion (PCS) and net heat of combustion (PCI).

[0034] EN ISO 13823:2020 is a test method for determining the fire responsiveness of building products (excluding flooring materials) to heat attack from single-burning materials (SBI).

[0035] The thickness of thermoplastic elastomer films is determined by ASTM D6988-21. Example

[0036] The following describes the production of flame-retardant and weather-resistant barrier laminates. The base sheet is E / ECR (corrosion-resistant E-glass) glass mat, which is a plain-weave fabric with leno weft and a basis weight of approximately 362 gsm and an organic content of 1.0 wt% (ash / glass content 99.0 wt%) as determined by TGA according to ASTM E1131-20. The base sheet further has a total heat of combustion (PCS) value of 0.234 MJ / kg according to EN ISO1716. A thermoplastic polyurethane (TPU) film (Platilon® U) with a basis weight of 28 gsm is then attached to the glass mat using a polyurethane (PU) adhesive applied using a discontinuous dot bonding method. Specifically, the PU adhesive is a one-component reactive hot-melt adhesive and is applied in an amount of approximately 5 gsm as discontinuous areas in a uniform dot pattern, wherein the areal density of the base sheet is covered by the adhesive at 35%, leaving approximately 65% ​​of the area between the base sheet and the film unattached. After the adhesive is applied, a set of pressure rollers is used to attach or laminate the film to the base sheet; then the adhesive is allowed to cure. According to EN ISO 1716, the final flame-retardant and weather-resistant barrier laminate has a width of 1.5 m, a basis weight of 395 gsm, and total heat of combustion (PCS) values ​​of 2.839 MJ / kg and 1.127 MJ / sqm. Table 1 provides the test results and subsequent findings for this laminate. Unless otherwise provided herein, any version of any standard or method mentioned herein is the most recently approved version as of the date of this application.

[0037] Table 1

[0038] .

Claims

1. A fire barrier membrane comprising: a base sheet comprising glass fibers, the base sheet having a basis weight of 296 to 420 grams per square meter, the base sheet having a maximum organic content of 1.5 weight percent; and a thermoplastic elastomer film attached to the base sheet, the film having a basis weight of 20 to 35 grams per square meter; wherein the thermoplastic elastomer film is attached to the base sheet by use of an adhesive that is discontinuously present between the film and the sheet at an areal density of 25% to 40% and the adhesive is present in an amount of 4 to 6 grams per square meter; and wherein the fire barrier membrane has a total heat of combustion (PCS) of less than 3 MJ / kg and less than 4 MJ / sqm as measured according to EN ISO 1716.

2. The flame retardant film of claim 1, wherein, the base sheet having a basis weight of 360 to 385 grams per square meter.

3. The flame-retardant film according to claim 1 or 2, wherein the base sheet having a total heat of combustion (PCS) of less than 0.38 MJ / kg as measured according to EN ISO 1716.

4. The flame-retardant film according to any one of claims 1 to 3, wherein, the base sheet is a plain weave glass fabric.

5. The flame-retardant film according to any one of claims 1 to 4, wherein, the base sheet comprises E-glass.

6. The flame-retardant film according to any one of claims 1 to 5, wherein the thermoplastic elastomer film has a basis weight of 25 to 31 grams per square meter.

7. The flame-retardant film according to any one of claims 1 to 6, wherein the thermoplastic elastomer film comprises a thermoplastic polyurethane (TPU), a thermoplastic copolyester (TPE-E), a thermoplastic polyamide (TPE-A), or a mixture thereof.

8. The flame retardant film of claim 7, wherein, the thermoplastic elastomer film comprises a polyester or polyether glycol based aromatic polyurethane polymer.

9. The flame-retardant film of any one of claims 1 to 8, wherein, the thermoplastic elastomer film is a monolithic film.

10. The flame-retardant film of any one of claims 1 to 9, wherein, the adhesive is discontinuously present between the film and the sheet at an areal density of 30% to 35%.

11. The flame-retardant film of any one of claims 1 to 10, wherein, the adhesive is discontinuously present as adhesive dots.

12. The flame-retardant film of any one of claims 1 to 11, wherein, the adhesive is a polyurethane.

13. The fire barrier membrane of any one of claims 1 to 12 having a water vapor diffusion equivalent air thickness (Sd value) of less than 0.12 as measured by EN ISO 12572.

14. The flame-retardant film of any one of claims 1 to 13, wherein, the fire barrier membrane shows no signs of water penetration after exposure to 200 mm of water column for 2 hours according to EN 1928 (Method A).

15. The flame-retardant film of any one of claims 1 to 13, wherein, The flame-retardant film showed no signs of water penetration after exposure to 200 mm of water column for 2 hours according to EN 1928 (Method A) after at least 5000 hours of UV aging corresponding to 800 MJ / m 2 at 50°C according to EN 1297.

16. The fire barrier membrane of any one of claims 1 to 15 having a European classification A2 fire rating according to EN 13501-1.

17. A facade or wall system comprising a plurality of layered sections of the fire barrier membrane of any one of claims 1 to 16 sealed with tape having a total heat of combustion (PCS) of less than 7.4 MJ / kg and less than 1.6 MJ / sqm as measured according to EN ISO 1716, wherein an edge of a first layered section of the fire barrier membrane overlaps a second layered section of the fire barrier membrane by at least 100 mm, and wherein the total areal surface coverage of the tape on the facade or wall system is 5.4% or less.

18. The facade or wall system of claim 17 further comprising a plurality of layered sections of a vapor barrier film also sealed with tape, wherein an edge of a first layered section of the vapor barrier film overlaps a second layered section of the vapor barrier film by at least 100 mm, and wherein the facade or wall system has an outer surface and an inner surface, and the layered section of the vapor barrier film is closer to the inner surface than the layered section of the flame retardant film.

19. Façade or wall system according to claim 18, wherein the vapor barrier film has a total heat of combustion (PCS) of less than 0.51 MJ / kg and less than 0.1 MJ / sqm, and wherein the total area surface coverage of the tape on the vapor barrier film is 5.4% or less. the vapor barrier film has a total heat of combustion (PCS) of less than 0.51 MJ / kg and less than 0.1 MJ / sqm, and wherein the total area surface coverage of the tape on the vapor barrier film is 5.4% or less.