Fire protection laminate

Abstract

A fire protection laminate (3) comprising the following layers in the indicated order: - an inorganic fiber layer, consisting of silicate glass fibers; - a fire protection silicone rubber layer and an adhesive compound layer, the adhesive compound being an acrylate adhesive compound that contains at least one fire protection component selected from aluminum oxides and aluminum hydroxides, has excellent fire protection properties and is particularly suitable for protection of storage batteries.

Description

[0001] Fire protection laminate

[0002] The invention relates to a fire protection laminate used to secure flammable objects, such as battery packs in electric vehicles, and to the use of such fire protection laminates.

[0003] As part of the transition to more environmentally friendly energy sources, rechargeable batteries (also known as secondary batteries or accumulators, or accumulators for short) are rapidly gaining importance. They are used not only in smaller electrical devices but also in electric vehicles, for example. Lithium-ion batteries have become particularly popular as rechargeable batteries.

[0004] Despite all the advantages of lithium-ion batteries, a major problem is the potential for mechanical damage to the batteries, which can lead to internal electrical short circuits and overheating. Errors during the charging process can also cause excessive heating. If the heating exceeds a certain limit and spreads throughout the battery, a condition known as thermal runaway occurs. The exothermic reaction taking place in the battery is continually accelerated by the generated heat, releasing ever more heat. This can lead to a fire in the battery, especially if the generated heat is so great that the plastic surrounding the battery melts and ignites.

[0005] This poses a significant risk, particularly in the case of electrically powered vehicles, if the entire vehicle catches fire, especially since the batteries are located beneath the passenger compartment. Therefore, if a fire starts in the battery area, it is essential to prevent or at least delay the fire from spreading to the passenger compartment and endangering the vehicle's occupants. According to Amendment 20 to the Global Technical Regulation on Electric Vehicle Safety (EVS), introduced in 2018, battery systems must withstand a thermal runaway event, if the event cannot be stopped, for at least five minutes after a warning that a thermal runaway has occurred. This must be done before the battery systems catch fire, the batteries explode, or smoke enters the passenger compartment, giving occupants the opportunity and sufficient time to escape.

[0006] The current state of the art offers various approaches to solving this problem. In addition to preventing thermal runaway altogether by taking every possible step to prevent short circuits, numerous solutions have been proposed, such as encasing the batteries or providing them with a housing to contain flames.

[0007] Battery systems are typically enclosed in a steel or aluminum housing. Since these alone often do not meet the requirements described above, numerous thermal protection and barrier elements are described in the prior art that can contain a fire or explosion for a sufficiently long time.

[0008] The use of fiberglass materials is particularly important here. US 2005 / 0170238 A1 describes a battery housing made of a glass-fiber-reinforced polymer. Furthermore, WO 2014 / 053623 describes a battery housing with a flexible shell made of endothermic heat-absorbing material and a tubular exhaust pipe with a covering made of temperature-resistant textile.

[0009] Many laminates proposed for fire protection also contain glass fibers or glass fiber fabrics in one form or another.

[0010] CN 207028393 U discloses a laminate consisting of a fabric layer, in particular glass fabric, nylon or polyester fabric, a silicone-ceramic-silicone rubber layer, and an adhesive layer. WO 2021 / 144758 A1 describes a multilayer thermal barrier device with a core layer comprising a plurality of fibers (in particular glass fibers) or a flame-retardant foam, and a further layer applied to or integrated into the core layer. This layer is intended to have low thermal conductivity and also consists of inorganic fibers or inorganic binders with inorganic fillers. Additional layers, e.g., of silicone resins, acrylates, or urethanes, may be provided.

[0011] WO 2020 / 070275 A1 discloses a composite system consisting of a carrier layer made of glass fiber fleece or fabric, an adhesive layer made of a thermoplastic polymer (synthetic rubber, water glass, polyurethane, or acrylate), and a fire-protection layer made of glass fiber fleece or fabric with an ablative coating, for which various minerals are proposed. Additionally, a stainless steel foil can be provided as an intermediate layer.

[0012] The problem is that the requirements for a material to stop or delay the effects of thermal runaway are very high. High pressure builds up inside the battery until the cell finally bursts. The temperatures that arise are enormous and can reach over 1,000°C. To make matters worse, in the case of vehicle batteries the available space is often very limited and, depending on the design, the fire protection material can in many cases only have a very thin layer. This means that there is often only 1-3 mm of free space available into which a fire protection material can be inserted. While many materials with a thickness of 3 mm still meet the fire protection requirements, this is often no longer the case for thicknesses below 3 mm or even 2 mm and less.

[0013] Finally, the precise application of a fire-resistant laminate is not easy, as conventional laminates are often stiff and tend to expand. Once affixed, the prior art composite systems typically cannot be removed to correct incorrect positioning. Furthermore, many of the existing laminates are very stiff and therefore difficult to apply.

[0014] The object of the present invention is therefore to provide a fire-protection laminate that meets the requirements of fire protection regulations, in particular, to comply with the five-minute time period that must elapse between thermal runaway and an explosion, an open fire, and / or smoke development in the passenger compartment, while having a total thickness of less than 3 mm. Furthermore, the fire-protection laminate should be easy to apply and, if possible, not be so firmly fixed to the substrate during application that it cannot be repositioned.

[0015] This object is achieved by a fire-protection laminate as described in the independent claim. The dependent claims relate to advantageous developments of the subject matter of the invention. Furthermore, the invention encompasses the use of the laminate according to the invention.

[0016] Accordingly, the invention relates to a fire protection laminate of the type mentioned above, which comprises the following layers in the specified sequence:

[0017] - an inorganic fiber layer consisting of silicate glass fibers; a flame-retardant silicone rubber layer; and an adhesive layer, wherein the adhesive is an acrylate adhesive containing at least one flame-retardant component selected from aluminum oxides and aluminum hydroxides.

[0018] Such a fire-protection laminate according to the invention exhibits very good fire protection properties and makes it possible to prevent or at least delay an open fire, even with a very thin layer thickness of 2 mm or less. Various test methods are used to verify the fire protection properties, in particular the so-called burning test and the battery impact test.

[0019] The test setup for the burning test is shown in Fig. 1. The laminate to be tested is placed between a 0.7 mm thick steel plate with a KTL (cathodic dip coating), simulating the casing of a vehicle battery, and a butane gas flame at a temperature of 1,200°C. The 1,200°C flame acts on the test setup for 10 minutes. During this time, the temperature on the side facing away from the flame, the "cold side," should not exceed 300°C. The battery impact test simulates the short-circuit phase of a battery, during which the very high temperatures not only cause a fire but also release hot particles. This scenario is simulated using a firework. For 22 seconds, a 22 mm caliber firework is fired from a distance of 20 mm at a 2 mm thick aluminum plate, onto which the laminate to be tested is applied. The test setup is shown in Fig. 2.The test is passed if the firework does not burn through the aluminum plate during the 22-second firing.

[0020] Both test procedures are described in detail in conjunction with the examples. Other test procedures relevant to testing the fire protection properties of batteries are also listed there.

[0021] In a particularly advantageous embodiment of the present invention, the silicate glass fibers of the fire-protection laminate have a silica content of at least 94%, in particular at least 96%. Such fibers exhibit particularly high temperature stability. Depending on the weave structure, the fibers can withstand temperatures of up to approximately 1,100 to 1,200°C.

[0022] The inorganic fiber layer can be in the form of knitted fabrics, non-woven fabrics, ribbons, braids, needle-punched textiles, felts, woven fabrics (including plain weave, twill, and satin weave), warp-knitted fabrics (including warp-knitted fabrics and knits), or nonwovens, whereby "nonwoven" is understood to mean at least textile fabrics according to EN 29092 (1988) as well as stitch-bonded nonwovens and similar systems. Furthermore, spacer fabrics and warp-knitted fabrics with lamination can be used. Such spacer fabrics are disclosed in EP 0 071 212 B1. Spacer fabrics are mat-shaped laminates with a cover layer made of a fiber or filament nonwoven, a backing layer, and, between these layers, individual or tufts of holding fibers that are needle-punched through the particle layer and are distributed over the surface of the laminate and interconnect the cover layer and the backing layer.

[0023] The inorganic fiber layer made of silicate glass fibers is particularly preferably a fabric in satin weave, in particular in the 12 H, 8 H or 8 / 3 version. The warp preferably has a thread count of 16 to 20 cm' 1 , the shot 12 to 16 cm' 1 A fabric with an 8 H satin weave and a warp thread count of 19 cm is particularly preferred. -1 , shot 14 cm' 1 Such a fabric is particularly temperature-stable and resistant to the mechanical stress caused by the hot particles.

[0024] It is particularly preferred if the flame-retardant silicone rubber layer consists of silicone rubber containing at least one type of particle selected from iron(III) oxide, ammonium polyphosphate, zinc borate, and aluminum hydroxide. These particles increase the temperature stability of the silicone rubber and thus improve the fire protection properties of the laminate.

[0025] There are various options for applying the silicone rubber layer. The flame-retardant silicone rubber layer is advantageously applied to the inorganic fiber layer using a liquid calendering process. This ensures an even application, which is particularly important given the thin layer thickness. Applying too thinly in individual areas would compromise the overall protection. Applying too thickly, on the other hand, would prevent the layer from being inserted into the available space. The liquid calendering process ensures that the silicone rubber penetrates the fabric to a certain extent, thus creating a stronger bond and densifying the composite, which improves the fire protection properties.

[0026] Numerous compounds can be used as flame-retardant components in the adhesive layer, such as the particles also mentioned for the silicone rubber layer, selected from iron(III) oxide, ammonium polyphosphate, zinc borate, and aluminum hydroxide. Furthermore, boron nitride is also used. However, the flame-retardant component in the adhesive layer is particularly preferably at least one compound selected from α-Al2O3, γ-Al2O3, α-Al(OH)3, γ-Al(OH)3, α-AlO(OH), or γ-AlO(OH), with α-Al2O3 and α-Al(OH)3 being particularly preferred because they have a very strong temperature-reducing effect. The compounds react by forming water vapor, which finds its way out of the adhesive. The resulting water vapor settles between the laminate and the surface (e.g., the housing surrounding the battery pack) to which it is attached. This creates a buffer layer with poor thermal conductivity, which means that the back of the surface is heated less.The acrylate adhesive is particularly preferably a pressure-sensitive adhesive. In the present application, a pressure-sensitive adhesive is understood, as is common parlance, to mean a substance that is permanently tacky and adhesive, at least at room temperature. A characteristic of a pressure-sensitive adhesive is that it can be applied to a substrate by pressure and remains adhered there, whereby the pressure to be applied and the duration of this pressure are not defined in more detail. In general, but fundamentally dependent on the exact type of pressure-sensitive adhesive, the temperature and humidity, as well as the substrate, the application of short-term, minimal pressure, which does not go beyond a light touch for a brief moment, is sufficient to achieve the adhesion effect; in other cases, a longer exposure duration of higher pressure may be necessary.

[0027] Pressure-sensitive adhesives have characteristic viscoelastic properties that lead to their permanent tack and adhesive strength. They are characterized by the fact that, when mechanically deformed, both viscous flow processes and the development of elastic restoring forces occur. The respective proportions of both processes are in a specific relationship to each other, depending on the precise composition, structure, and degree of crosslinking of the pressure-sensitive adhesive, as well as the speed and duration of the deformation and the temperature. The proportional viscous flow is necessary to achieve adhesion. Only the viscous components, caused by macromolecules with relatively high mobility, enable good wetting and flow onto the substrate to be bonded.A high proportion of viscous flow leads to high pressure-sensitive adhesion (also referred to as tack or surface stickiness) and thus often also to high adhesive strength. Highly cross-linked systems, crystalline, or glass-like polymers, are generally not, or at least only slightly, tacky due to the lack of flowable components.

[0028] The proportional elastic restoring forces are necessary to achieve cohesion. They are caused, for example, by very long-chain and highly entangled as well as physically or chemically cross-linked macromolecules and enable the transfer of the forces acting on an adhesive bond. They mean that an adhesive bond can sufficiently withstand a permanent load acting on it, for example in the form of permanent shear stress, over a longer period of time. A “poly(meth)acrylate” is understood to be a polymer which is obtainable by free-radical polymerization of acrylic and / or methacrylic monomers and, if appropriate, other copolymerizable monomers. In particular, a “poly(meth)acrylate” is understood to be a polymer whose monomer base consists of at least 50 wt.-% of acrylic acid, methacrylic acid, acrylic acid esters and / or methacrylic acid esters, wherein acrylic acid esters and / or methacrylic acid esters are present at least proportionally, preferably at least 30 wt.%, based on the total monomer base of the polymer in question.

[0029] The pressure-sensitive adhesive preferably contains poly(meth)acrylates in a total amount of 30 to 60 wt. %, more preferably in a total amount of 35 to 45 wt. %, based in each case on the total weight of the pressure-sensitive adhesive. It may contain a (single) poly(meth)acrylate or multiple poly(meth)acrylates. References above and below to "the poly(meth)acrylate" are always intended to include the presence of multiple poly(meth)acrylates; likewise, references to "the poly(meth)acrylates" or "all poly(meth)acrylates" are also intended to include the presence of only a single poly(meth)acrylate.

[0030] The glass transition temperature of the poly(meth)acrylate of the pressure-sensitive adhesive of the invention is preferably <0°C, more preferably between -25 and -70°C. The glass transition temperature of polymers or of polymer blocks in block copolymers is determined according to the invention by means of dynamic scanning calorimetry (DSC). For this purpose, approximately 5 mg of an untreated polymer sample is weighed into an aluminum crucible (volume 25 μl) and sealed with a perforated lid. A DSC 204 F1 from Netzsch is used for the measurement. The measurement is carried out under nitrogen for inerting. The sample is first cooled to -150°C, then heated at a heating rate of 10 K / min to +150°C and cooled again to -150°C. The subsequent second heating curve is again run at 10 K / min, and the change in heat capacity is recorded. Glass transitions are recognized as steps in the thermogram.

[0031] The poly(meth)acrylate of the pressure-sensitive adhesive can preferably be composed of the following monomers: n-butyl acrylate, n-butyl methacrylate, n-pentyl acrylate, n-pentyl methacrylate, n-amyl acrylate, n-hexyl acrylate, n-hexyl methacrylate, n-heptyl acrylate, n-octyl acrylate, n-octyl methacrylate, n-nonyl acrylate, isobutyl acrylate, isooctyl acrylate, isooctyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, 2-propylheptyl acrylate and 2-propylheptyl methacrylate, acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, aconitic acid, dimethylacrylic acid, ß-acryloyloxypropionic acid, Trichloroacrylic acid, vinylacetic acid, vinylphosphonic acid, maleic anhydride, hydroxyethyl acrylate, in particular 2-hydroxyethyl acrylate, hydroxypropyl acrylate, in particular 3-hydroxypropyl acrylate, hydroxybutyl acrylate, in particular 4-hydroxybutyl acrylate, hydroxyhexyl acrylate, in particular 6-hydroxyhexyl acrylate, hydroxyethyl methacrylate, in particular 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate,insbesondere 3-Hydroxypropylmethacrylat, Hydroxybutylmethacrylat, insbesondere 4-Hydroxybutylmethacrylat, Hydroxyhexylmeth- acrylat, insbesondere 6-Hydroxyhexylmethacrylat, Allylalkohol, Glycidylacrylat, Glycidyl- methacrylat, Methylacrylat, Ethylacrylat, Propylacrylat, Methylmethacrylat, Ethylmeth- acrylat, Benzylacrylat, Benzylmethacrylat, sec-Butylacrylat, tert-Butylacrylat, Phenyl- acrylat, Phenylmethacrylat, 4-Acryloylmorpholin, Isobornylacrylat, Isobornylmethacrylat, tert-Butylphenylacrylat, tert-Butylaphenylmethacrylat, Dodecylmethacrylat, Isodecyl- acrylat, Laurylacrylat, n-Undecylacrylat, Stearylacrylat, Tridecylacrylat, Behenylacrylat, Cyclohexylmethacrylat, Cyclopentylmethacrylat, Phenoxyethylacrlylat, Phenoxyethylmeth- acrylat, 2-Butoxyethylmethacrylat, 2-Butoxyethylacrylat, 3,3,5-Trimethylcyclohexylacrylat, 3,5-Dimethyladamantylacrylat, 4-Cumylphenylmethacrylat, Cyanoethylacrylat, Cyano- ethylmethacrylat, 4-Biphenylacrylat, 4-Biphenylmethacrylat, 2-Naphthylacrylat,2- Naphthylmethacrylat, Tetrahydrofufurylacrylat, Diethylaminoethylacrylat, Diethylamino- ethylmethacrylat, Dimethylaminoethylacrylat, Dimethylaminoethylmethacrylat, 3- Methoxyacrylsäuremethylester, 3-Methoxybutylacrylat, 2-Phenoxyethylmethacrylat, Butyl- diglykolmethacrylat, Ethylenglycolacrylat, Ethylenglycolmonomethylacrylat, Methoxypoly- ethylenglykolmethacrylat 350, Methoxypolyethylenglykolmethacrylat 500, Propylenglycol- monomethacrylat, Butoxydiethylenglykolmethacrylat, Ethoxytriethylenglykolmethacrylat, Octafluoropentylacrylat, Octafluoropentylmethacrylat, 2,2,2-T rifluorethylmethacrylat,

[0032] 1 .1 .1 .3.3.3-Hexafluoroisopropylacrylat, 1 ,1 ,1 ,3,3,3-Hexafluoroisopropylmethacrylat,

[0033] 2.2.3.3.3-Pentafluoropropylmethacrylat, 2,2,3,4,4,4-Hexafluorobutylmethacrylat,

[0034] 2,2,3,3,4,4,4-Heptafluorobutylacrylat, 2,2,3,3,4,4,4-Heptafluorobutylmethacrylat,

[0035] 2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-Pentadecafluorooctylmethacrylat, Dimethylaminopropylacrylamid, Dimethylaminopropylmethacrylamid, N-(1 -Methylundecyl)acrylamid, N-(n- Butoxymethyl)acrylamid, N-(Butoxymethyl)methacrylamid, N-(Ethoxymethyl)acrylamid, N- (n-Octadecyl)acrylamid; N,N-Dialkyl-substituierte Amide wie beispielsweise N,N- Dimethylacrylamid und N,N-Dimethylmethacrylamid; N-Benzylacrylamid, N- Isopropylacrylamid, N-tert-Butylacrylamid, N-tert-Octylacrylamid, N-Methylolacrylamid, N- Methylolmethacrylamid, Acrylnitril, Methacrylnitril; Vinylether wie Vinylmethylether, Ethylvinylether, Vinylisobutylether; Vinylester wie Vinylacetat; Vinylhalogenide, Vinylidenhalogenide, Vinylpyridin, 4-Vinylpyridin, N-Vinylphthalimid, N-Vinyllactam, N- Vinylpyrrolidon, Styrol, a- und p-Methylstyrol, a-Butylstyrol, 4-n-Butylstyrol, 4-n-Decylstyrol, 3,4-Dimethoxystyrol;

[0036] The adhesive can be chemically crosslinked using state-of-the-art technology. This can be achieved using various mechanisms, such as electron beam curing, UV crosslinking, and thermal crosslinking. UV crosslinking is particularly popular, using commercially available photoinitiators such as benzoin acrylate or phenyl ketones.

[0037] The polymerization of the (meth)acrylate monomers is preferably UV-initiated and only takes place up to a degree of polymerization at which a mixture of polymers and monomers is present. This – usually syrupy – mixture is then compounded with the other components of the pressure-sensitive adhesive and only after the compound has been formed into a sheet is it further polymerized or crosslinked by UV irradiation. Therefore, the finished (fully polymerized) polymers are not used in the compounding of the pressure-sensitive adhesive, but rather a mixture of polymers and monomers, with the monomers also serving as a solvent for the polymers.

[0038] Particularly preferred is an acrylic pressure-sensitive adhesive produced by UV-initiated bulk polymerization. Such adhesives are particularly easy to handle and apply.

[0039] The acrylic pressure-sensitive adhesive is further preferably a pressure-sensitive adhesive that contains a. at least one poly(meth)acrylate; and b. at least 40 wt. %, based on the total weight of the pressure-sensitive adhesive, of flame-retardant component in the adhesive layer, which may be a single filler or a mixture of at least two fillers, wherein the mixture of at least two fillers comprises at least one filler consisting of substantially round particles. "Round" here means that the particles have no corners or edges.

[0040] The preferred pressure-sensitive adhesive preferably contains the flame-retardant component in an amount of at least 50% by weight, more preferably at least 55% by weight, in each case based on the total weight of the pressure-sensitive adhesive.

[0041] If the preferred pressure-sensitive adhesive contains a mixture of at least two fillers to at least 50% by weight, said mixture containing at least one filler Fi sph, which consists of essentially round particles, it has been shown that such a filler mixture is able to bring about certain properties of the adhesive tape largely independently of direction, i.e. to counteract anisotropy.

[0042] The filler mixture preferably results in a thermal conductivity of the pressure-sensitive adhesive that is weakly or not at all anisotropic. The filler mixture thus preferably comprises at least one thermally conductive filler. In particular, at least the filler consisting of essentially round particles is a thermally conductive filler.

[0043] The preferred rounded filler also has a low electrical conductivity, so that the filler in question, in addition to thermal conductivity, exhibits properties of an electrical insulator or imparts properties of an electrical insulator to the pressure-sensitive adhesive.

[0044] Electrically insulating properties are also desirable for the additional filler in the filler mixture of the preferred pressure-sensitive adhesive. In particular, the entirety of the fillers in the pressure-sensitive adhesive is electrically insulating. The pressure-sensitive adhesive is particularly preferably electrically insulating.

[0045] An electrical insulator is a substance that has a specific resistance of > 10 8 Q*cm according to TRGS 727.

[0046] Preferably only the filler Fi sp h consists of essentially round particles and is present in excess of the other filler or the total of the other fillers. The filler Fi sp h consists in particular of aluminum hydroxide, or thus of essentially round aluminum hydroxide particles.

[0047] Most preferably, the mixture consists of two fillers of aluminum hydroxide and aluminum oxide, wherein the aluminum hydroxide is in the form of substantially round particles.

[0048] Depending on the application area and the desired properties of the pressure-sensitive adhesive, it may contain additional components and / or additives, either alone or in combination with one or more other additives or components.

[0049] The pressure-sensitive adhesive may contain at least one tackifier, which can also be referred to as an adhesion promoter or adhesive resin. According to the general understanding of those skilled in the art, a "tackifier" is an oligomeric or polymeric resin that increases the autohesion (tack, inherent stickiness) of the pressure-sensitive adhesive compared to an otherwise identical pressure-sensitive adhesive that does not contain a tackifier.

[0050] In one embodiment, the pressure-sensitive adhesive may contain colorants, in particular pigments and / or carbon black.

[0051] Preferably, the inorganic fiber layer is pretreated before applying the flame-retardant silicone rubber layer, with the pretreatment being a corona treatment, plasma treatment, or the application of a primer. Such pretreatment ensures a particularly good bond between the inorganic fiber layer and the flame-retardant silicone rubber layer, which is of great importance in the laminate according to the invention, since the layers must remain bonded to one another even under very high heat exposure.

[0052] In a further advantageous embodiment, the flame-retardant silicone rubber layer is pretreated before applying the adhesive layer, with the pretreatment being a corona treatment, plasma pretreatment, or the application of a primer. Corona treatment is preferably used. Here, too, pretreatment ensures a particularly good bond, specifically between the flame-retardant silicone rubber layer and the adhesive layer. Regarding the importance of a good bond between the layers, the above applies.

[0053] The laminate can have any thickness. However, it has the great advantage that it offers very good fire protection even with a very small overall thickness. The entire laminate advantageously has a thickness of 0.5 to 2.5 mm, preferably 0.5 to 2 mm and particularly preferably 0.8 to 1.5 mm. The thickness of the inorganic fiber layer is preferably 0.2 to 1.3 mm, particularly preferably 0.3 to 0.9 mm and very particularly preferably 0.3 to 0.7 mm. The flame-retardant silicone rubber layer preferably has a thickness of 0.35 to 1.8 mm, particularly preferably 0.35 to 1.2 mm and very particularly preferably 0.35 to 0.9 mm. The thickness of the adhesive layer is preferably from 0.05 to 0.15 mm, particularly preferably from 0.05 to 0.13 mm and most preferably from 0.1 to 0.125 mm.

[0054] In a particularly preferred embodiment, the laminate according to the invention comprises only the three layers, i.e. the inorganic fiber layer, the flame-retardant silicone rubber layer and the adhesive layer with flame-retardant component.

[0055] It is possible to further improve the mechanical properties of the inorganic fiber layer, especially in the event of fire, through an additional coating. In a further advantageous embodiment, a silicone-based layer is applied to the side of the inorganic fiber layer facing away from the flame-retardant silicone rubber layer. The surface weight of this silicone-based layer is advantageously between 5 and 50 g / m². 2 .

[0056] In addition, the adhesive layer is covered with a release liner.

[0057] The laminate according to the invention can be used in a wide range of fire protection applications. The laminate is particularly suitable as fire protection for batteries, especially lithium-ion batteries. Furthermore, the laminate is particularly suitable for use in accumulators for electric vehicles.

[0058] When a short circuit occurs in such batteries, very high pressure initially builds up in the cell until it bursts through pressure relief valves. For a few seconds, in addition to a "normal flame," there is a violent discharge of particles comparable to fireworks. This particle bombardment typically lasts between 15 and 25 seconds, depending on the battery type.

[0059] Accumulator or battery packs are usually housed in a housing, often made of aluminum or steel with a cataphoretic dip coating. Such a housing can withstand particle bombardment for 4 to 5 seconds, after which it melts, and the particle bombardment and flames escape to the outside. The laminate according to the invention is preferably applied to the inside of the housing, in particular glued under the lid of the housing. If the laminate is applied to the inside of the housing, the duration by which the enclosure can withstand this particle bombardment can be significantly extended. The length of time by which the withstand time is extended depends on the thickness of the laminate or its layers. For example, a laminate according to the invention with a layer thickness of 2 mm can withstand the 22 seconds that particle bombardment usually lasts for lithium-ion batteries, so that the escape of flames and thus the spread of the fire can be prevented.

[0060] The laminate according to the invention thus provides adequate fire protection despite its very thin layer thickness. This is particularly advantageous because the space available for an electric vehicle battery is very limited. Ideally, the laminate should be attached inside the housing, on the cover facing the passenger compartment. The available space is typically a maximum of 2 mm, and in some cases, even less (less than 1.5 mm or even less than 1.3 mm).

[0061] Many conventional fire-resistant laminates are very rigid, making positioning difficult. The laminate according to the invention is also particularly advantageous because it is flexible and therefore easy to apply. Furthermore, the laminate according to the invention is repositionable due to the pressure-sensitive adhesive used. This means that even if the application is not successful in the desired position the first time, this is not critical because it can be peeled off and repositioned. Examples:

[0062] The following exemplary experiments are intended to explain the invention in more detail, without wishing to unnecessarily restrict the invention through the choice of the given examples.

[0063] Measurement methods:

[0064] Burning test

[0065] The test setup for the burning test is shown in Fig. 1. The laminate to be tested (3) (test piece size: 70 x 150 mm) is placed between a 0.7 mm thick steel plate with a cathodic dip coating (1), which simulates the casing of a vehicle battery, and a butane gas flame (2) with a temperature of 1,200°C. The 1,200°C flame acts on the test setup for 10 minutes. During this time, the temperature on the side facing away from the flame, the “cold side” (4), should not exceed 300°C. The temperature on the cold side (4) and the “hot side” (5) is monitored using temperature sensors (6).

[0066] Butane gas is used as the fuel, and the burner output is 1.85 kW. This type of burner accurately simulates the conditions observed during a lithium-ion battery fire. The temperature sensors are type K thermocouples for the cold side and type K or type B thermocouples for the hot side.

[0067] Batterieeinschlagtest (Battery Impact Test)

[0068] The battery impact test simulates the short circuit phase of a battery, during which not only a fire starts due to the very high temperatures, but also hot particles are released. The test setup is shown in Fig. 2. This scenario is simulated using a firework (7). For 22 seconds, a 22 mm caliber firework is fired at a distance of 20 mm from the sample at a 2 mm thick aluminum plate (1 ), on which the laminate to be tested (3) (size of the test piece: 150 x 150 mm) is applied. The result is given as the time in seconds that the laminate withstands the impact before breakthrough occurs. The test is passed if the firework does not burn through the aluminum plate (1 ) during the 22-second exposure. Aluminum is particularly suitable for this test because it begins to melt at a temperature of 660 °C and thus makes the test result clearly visible if the firework burns through the plate.

[0069] Flame test

[0070] The burning behavior of the test specimen after exposure to flame is determined according to UL94V. The burning and afterglow times, as well as the burning droplets from the test specimen and whether any droplets ignite a cotton indicator located beneath the test specimen, are evaluated in a vertical orientation of the test specimen. The test specimen measures 125 x 13 x 1.2 (mm). 3 are exposed to flame with a Bunsen burner, twice for 10 seconds. Fire-resistant laminates according to the invention must meet the UL94V0 standard (extinction of a vertically clamped sample within 10 seconds without burning droplets of molten plastic and a maximum of 30 seconds of afterglow).

[0071] Preparation of samples

[0072] Production of laminates

[0073] To produce a laminate according to the invention, the standard transfer adhesive tape tesa 58394 was used and laminated together with a composite material POLOTSK-STEKLOVOLOKNO-600+Elastosil R501 / 75OH+2% ELASTOSIL® COLOR PASTE FL RED IRON OXIDE RAL 3013. The materials used for the comparative examples are listed in Table 1.

[0074] In this way, laminates with a layer thickness of 1.2 mm were produced. These were subjected to the burn test and, if the burn test results were promising, also to the battery impact test.

[0075] The results are summarized in Table 1 below:

[0076] Table 1

[0077] * Average of 5 individual values

[0078] ** Cold side temperature after 10 min, flame temperature 1200 °C, sample size 70 mm x 150 mm, measured vertically

[0079] *** Time to breakthrough

[0080] The majority of comparative examples 2-11 already demonstrate a lack of suitability in the burning test, as the temperature on the "cold side" far exceeds 300°C. Only the inventive laminate according to Example 1, with the glass fiber fabric insulation layer composite material POLOTSK-STEKLOVOLOKNO-600 + Elastosil R501 / 75OH + 2% ELASTOSIL® COLOR PASTE FL RED IRON OXIDE RAL 3013 and the adhesive tesa 58394, maintains a temperature below 300°C for the required 10 minutes, namely 278°C on the "cold side" facing away from the burner. Only in this case does the laminate provide sufficient insulation to prevent heating on the back of the aluminum layer.

[0081] In the battery impact test, the laminate according to Example 1 could only achieve 15 seconds, but with a slightly thicker laminate (2 mm instead of 1.2 mm) with otherwise identical components, the required 22 seconds were achieved.

Claims

Patent claims 1 . Fire protection laminate (3), comprising the following layers in the specified sequence: - an inorganic fiber layer consisting of silicate glass fibers; a flame-retardant silicone rubber layer; and an adhesive layer, wherein the adhesive is an acrylate adhesive containing at least one flame-retardant component selected from aluminum oxides and aluminum hydroxides.

2. Fire protection laminate (3) according to claim 1, characterized in that the silicate glass fibers have a silica content of at least 94%, in particular at least 96%.

3. Fire protection laminate (3) according to claim 1 or 2, characterized in that the inorganic fiber layer consists of silicate glass fibers, a fabric in satin weave, in particular in the 12 H, 8 H or 8 / 3 design.

4. Fire protection laminate (3) according to claim 1 or 2, characterized in that the flame-retardant silicone rubber layer consists of silicone rubber containing at least one type of particle selected from iron(III) oxide, ammonium polyphosphate, zinc borate and aluminum hydroxide.

5. Fire protection laminate (3) according to at least one of claims 1 to 4, characterized in that the flame-retardant silicone rubber layer is applied to the inorganic fiber layer by a liquid calendering process.

6. Fire protection laminate (3) according to at least one of claims 1 to 5, characterized in that the acrylate adhesive is an acrylate pressure-sensitive adhesive produced by UV-initiated bulk polymerization.

7. Fire protection laminate (3) according to at least one of claims 1 to 6, characterized in that the flame retardant component in the adhesive layer is at least one compound selected from a-AI2O3, y-AI2O3, a-AI(OH)3, y-AI(OH)3, a-AlO(OH) or y-AlO(OH).

8. Fire protection laminate (3) according to at least one of claims 1 to 7, characterized in that the inorganic fiber layer is pretreated before the application of the flame-retardant silicone rubber layer, wherein the pretreatment is a corona treatment or the application of a primer.

9. Fire protection laminate (3) according to at least one of claims 1 to 8, characterized in that the flame-retardant silicone rubber layer is pretreated before the application of the adhesive layer, wherein the pretreatment is a corona treatment or the application of a primer.

10. Fire protection laminate (3) according to at least one of claims 1 to 9, characterized in that the inorganic fiber layer has a thickness of 0.2 to 1.3 mm. 1 1. Fire protection laminate (3) according to at least one of claims 1 to 10, characterized in that the flame-retardant silicone rubber layer has a thickness of 0.35 to 1.8 mm.

12. Fire protection laminate (3) according to at least one of claims 1 to 11, characterized in that the adhesive layer has a thickness of 0.05 to 0.15 mm.

13. Fire protection laminate according to at least one of claims 1 to 12, characterized in that the entire laminate has a thickness of 0.5 to 2.5 mm.

14. Fire protection laminate (3) according to at least one of claims 1 to 13, characterized in that a silicone-based layer is applied to the side of the inorganic fiber layer facing away from the flame-retardant silicone rubber layer.

15. Use of the fire protection laminate (3) according to at least one of claims 1 to 14 as fire protection for batteries.

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