DE102016225906A1 - Adhesive tape with flame retardant properties - Google Patents

Abstract

By using an adhesive tape (2) which is flame-retardant for fixing a sleeve (1) surrounding an airbag (3), the safety of the airbag (3) is increased. In this case, a double-sided adhesive tape (2) can be used which consists of at least three layers, the at least three layers being the following layers: a) a first outer PSA layer b) a flame-retardant layer comprising at least one flame-retardant PSA layer at least 10% by weight, preferably from 15 to 35% by weight, of a flame retardant, andc) a second outer pressure-sensitive adhesive layer.

Description

The present invention relates to the use of an adhesive tape for fixing a sleeve surrounding an airbag and a double-sided adhesive tape, in particular for the above-mentioned use, wherein the adhesive tape preferably consists of at least three layers, and a sleeve, surrounding an airbag.

Airbags are an indispensable part of vehicles. In particular in motor vehicles and aircraft, they serve to protect the passengers against impact and today form an important part of their occupant restraint system on a regular basis. Airbags are also found in other areas, e.g. as avalanche airbags use. The airbag in a motor vehicle consists of a plastic bag, which unfolds in an accident within a few milliseconds with a loud bang between the occupant and parts of the vehicle interior. The triggering takes place by the ignition of a pyrotechnic propellant charge. The resulting combustion gases fill the airbag.

During installation, airbags are folded or rolled in order to be able to fit into the space provided or the compartment provided in the vehicle in a space-efficient manner. In order to prevent the airbags from deploying prior to installation or fitting, they are previously surrounded by a so-called sleeve and are then located in a type of pocket that prevents expansion or deployment. In order to effectively prevent expansion or deployment, it is necessary to close or fix the sleeve.

A sleeve in the sense of the present invention is thus an envelope with which airbags are encased. These sleeves are used to protect and fix the airbags to prevent accidental deployment of the airbags before installation and also before use.

As with all other components of a motor vehicle or aircraft, special requirements with regard to safety apply to airbags and thus also to the sleeves surrounding them, which also includes, for example, that the corresponding products are flame-retardant. Accordingly, the sleeve is made of a polyethylene or polypropylene in particular fleece, wherein the nonwoven fabric is flame retardant.

Flame retardant in the sense of the present invention means that the adhesive tape meets the requirements of FMVSS 302. The FMVSS 302 (Federal Motor Vehicle Safety Standard - No. 302) or the technically equivalent used in Europe, Canada and Japan Standard ISO 3795 describes the requirements for the fire resistance of materials used in the passenger compartment of motor vehicles (for example passenger cars, multipurpose passenger cars, lorries and buses). It serves to reduce the deaths and injuries of passengers in fires in motor vehicles, especially in vehicle fires that are triggered in the vehicle interior by, for example, matches or cigarettes.

A weak point in previous sleeves was the closure of the same. For this purpose, adhesive tapes, in particular double-sided adhesive tapes were used regularly. Conventional tapes do not meet the safety requirements described, since they can catch fire and burn with appropriate external exposure. This is not tolerable in light of the fact that an airbag is triggered by the ignition of a pyrotechnic propellant.

The present invention solves this problem by the adhesive tape is flame-retardant when using an adhesive tape for fixing a sleeve surrounding an airbag. This ensures that the sleeve is completely, i. including its closure, is resistant to flames, thus minimizing the risk of fire.

An "adhesive tape" is generally understood to mean a self-supporting system which is substantially extended in two spatial directions and is therefore to be designated as a sheet material which has a pressure-sensitive adhesive or (re) activatable adhesive on at least one of its two outwardly facing main surfaces and thus at least after activation Adhesive effect can develop. The term "adhesive tape" also covers systems which have already been bonded, but whose basic state is in accordance with the above definition. The term "adhesive tape" does not include liquid adhesives, not even in the cured and / or bonded state.

The adhesive tape according to the invention may preferably be formed both carrier-free, as also - particularly preferably - have at least one carrier which is coated on at least one side, preferably on both sides, with a flame-retardant PSA. It is particularly preferred if the carrier is designed as a stabilizing scrim.

In the case of a carrier-free adhesive tape, the flame-retardant PSA preferably contains at least 10% by weight of flame retardant, based on the total weight of the flame-retardant PSA layer. The pressure-sensitive adhesive layer particularly preferably comprises 10 to 35% by weight of flame retardant, more preferably 12 to 30% by weight of flame retardant, in particular 14 to 28% by weight of flame retardant, for example 17 to 26% by weight of flame retardant, in each case based on the total weight the pressure-sensitive adhesive layer.

In the case of the use of an adhesive tape with backing, it is particularly preferred if the flame-retardant PSA applied to at least one side contains at least 10% by weight of flame retardant, based on the total weight of the flame-retardant PSA layer. Preferably, the PSA layer 10 to 35 wt .-% flame retardant, more preferably 12 to 30 wt .-% flame retardants, especially 14 to 28 wt .-% flame retardants, for example 17 to 26 wt .-% flame retardants, each based on the total weight of flame-retardant pressure-sensitive adhesive layer. As a result, the flame retardancy properties of the adhesive tape are determined substantially, preferably completely, by the flame retardant contained in the outer pressure-sensitive adhesive layer or in the outer pressure-sensitive adhesive layers, whereas the inner support material does not necessarily have to have flame-retardant properties, which significantly increases the variability for the carrier material to be used. It has been found that it is sufficient to provide the external pressure-sensitive adhesive layer (s) with flame retardant to achieve adequate flame retardancy. Advantageously, this makes it possible to keep the carrier layer largely or completely free from being influenced by added flame retardant. Many, in particular mechanical, properties of the adhesive tape are fully realized in this way and are not mitigated in their manifestation by flame retardant additives.

In addition to airbags in motor vehicles, there are a large number of applications and constructions in which legislators place high demands on flame retardancy for materials used. Adhesives and adhesive tapes which are flame retardant are therefore used primarily in constructions which are subject to such increased safety requirements. These can be found u.a. in the transport sector, such as airplanes, trains, buses and elevators. Even in buildings, in particular those that are accessible to the public, it is often necessary to provide adhesive tapes used there in such a way that they are difficult or even non-flammable. Another example is computer technology, where more and more pressure-sensitive adhesive tapes are being used as part of a progressive miniaturization of components, while at the same time the demands on them are increasing. Even very high temperatures can occur in the circuits during operation. If soldered connections are also produced on the circuits, temperatures of 280 ° C. and more occur, at which existing adhesive tapes must not ignite.

The terms "flame retardance" and "flame retardancy" often also include indirect aspects such as reduced smoke and heat development as well as preventing or at least reducing the formation of harmful gases.

Pressure-sensitive adhesive tapes find versatile use in temporary or permanent bonds. Mostly they are used as mounting tapes to connect two substrates or components together. This requires a two-sided coating of the adhesive tape with adhesive. In addition, there are also single-sided pressure-sensitive adhesive tapes. Both sides adhesive pressure-sensitive adhesive tapes may be formed carrier-free or by both sides coated with pressure-sensitive adhesive carrier. Both coated and non-adhesive tapes may be covered with a liner to protect the adhesive layer after manufacture until final application. A liner is a cover but does not fall under the definition of "carrier". A carrier remains in the adhesive tape even after application.

Generally, pressure-sensitive adhesive tapes with carrier - whether single-sided or double-sided adhesive - are increasingly preferred because of the mechanical properties that can be adjusted over a wide range. The adjustability of the property profile is essentially due to the design of the carrier.

In the case of flame retardant adhesive tapes, it has been found that the adjustability of the property profile is severely restricted when the carrier contains flame retardant. Therefore beats the EP 16 179 112 to use a carrier material which contains no or only very little flame retardant, while the pressure-sensitive adhesive layer (s) applied to the carrier contains or contain at least 10% by weight of flame retardant.

However, for certain applications, for example also in the case of the sleeves for airbags according to the first aspect of the present invention, this results in that the adhesive properties of the pressure-sensitive adhesive for the bond are insufficient or at least capable of improvement. A further object of the present invention was therefore to provide a double-sided adhesive tape, in particular for use for the fixation of sleeves for airbags, wherein the adhesive tape consists of at least three layers, which enable a good and secure adhesion of the adhesive tape.

1. a) eine erste Haftklebemasseschicht
2. b) eine flammhemmende Schicht, umfassend mindestens eine flammhemmende Haftklebemasseschicht, die mindestens 10 Gew.-%, vorzugsweise von 15 bis 35 Gew.-%, eines Flammschutzmittels enthält, und
3. c) eine zweite Haftklebemasseschicht.

This object is achieved according to the invention in that the at least three layers are the following layers:

1. a) a first pressure-sensitive adhesive layer
2. b) a flame-retardant layer comprising at least one flame-retardant pressure-sensitive adhesive layer containing at least 10% by weight, preferably from 15 to 35% by weight, of a flame retardant, and
3. c) a second pressure-sensitive adhesive layer.

The combination of these three layers combines the positive properties of, first, the flame retardancy (layer b)) and the other good adhesion (layers a) and c)), so that a flame-retardant adhesive tape is obtained, which is also on more demanding substrates such Example airbag jacketing sleeves adheres well.

Particularly preferred is an embodiment in which the flame retardant layer b) further comprises a further flame retardant PSA layer containing at least 10 wt .-%, preferably 15 to 35 wt, of a flame retardant, and a stabilizing gel layer, wherein the stabilizing gel layer between the two flame-retardant PSA layers is arranged. The flame-retardant layer b) is thus itself a composite of three layers, a stabilizing gel layer and two interposed flame-retardant PSA layers. Particularly preferably, the stabilizing scrim is also made of flame retardant material. However, it is also possible that it is a non-flame retardant material. In this case, the flame-retardant pressure-sensitive adhesive layers are formed so as to ensure the flame-retardant properties for the entire adhesive tape.

In the case of a particularly suitable double-sided adhesive tape in the context of the present invention, the ratio of the basis weights of the flame-retardant layer to the sum of the basis weights of the two outer pressure-sensitive adhesive layers is at least 1: 1, preferably 2: 1 and particularly preferably 4: 1 the flame retardant layer can ensure that the entire tape has flame retardant properties and can meet the requirements in this regard. With such ratios, particularly good flame retardancy properties are thus achieved. It can be seen from the above that, if the adhesive tape has an outer pressure-sensitive adhesive layer on each side, the basis weight is understood to be the sum of the basis weights of both outer pressure-sensitive adhesive layers.

Very particular preference is given to an embodiment of the double-sided adhesive tape in which the two pressure-sensitive adhesive layers each have substantially the same basis weight and the flame-retardant layer has a basis weight which is substantially twice the basis weight of each of the two pressure-sensitive adhesive layers.

As stated above, in the case of flame-retardant adhesive tapes, it has been found that the adjustability of the property profile is severely restricted when the carrier contains flame retardant. A particularly good adhesive tape for a wide range of applications is therefore obtained by using a carrier material for the adhesive tape according to layer b) which contains no or only very little flame retardant, while the pressure-sensitive adhesive layer (s) applied to the carrier has at least 10% by weight .-% flame retardant contains or contain. This layer provides the flame retardant properties of the entire adhesive tape; the good bondability to the substrate is provided by the middle layer b) framing pressure-sensitive adhesive layers a) and c).

The double-sided flame retardant adhesive tape described above is particularly well suited for use in fixing a sleeve surrounding an airbag. It may be formed carrier-free or at least have a carrier. Decisive is the at least three-layered structure with a flame-retardant PSA layer and applied on both sides of this flame-retardant PSA layer pressure-sensitive adhesive layers that are not flame retardant, but ensure a good bondability on the substrate to be bonded. The flame-retardant PSA layer has such good flame-retardant properties that it ensures flame-retardancy for the two PSA layers surrounding it. This happens, for example, by mixing with the pressure-sensitive adhesive layers which melt in the event of a fire to give an overall flame-retardant mass.

Finally, the present invention also protects a sleeve surrounding an airbag, wherein the sleeve is closed with a double-sided adhesive tape according to the invention. Such a sleeve has the advantages mentioned above, namely it fulfills the above-mentioned requirements of the FMVSS 302 or the corresponding other national or supranational safety requirements.

As carriers in the context of the present invention, it is possible to use all known textile carriers such as knits, scrims, ribbons, braids, tufted textiles, felts, fabrics (comprising linen, twill and satin weave), knitted fabrics (comprising warp knitwear and knitwear) or nonwovens, wherein "Nonwoven" at least textile fabrics according to EN 29092 (1988) and stitchbonded nonwovens and similar systems are to be understood.

Also, lamination fabrics and knitted fabrics can be used. Such spacer fabrics are used in the EP 0 071 212 B1 disclosed. Spacer fabrics are mat-shaped laminates with a cover layer of a fibrous or filament nonwoven fabric, a backing layer and individual layers or tufts of retaining fibers present between these layers, which are needled through the particle layer distributed over the surface of the laminate body and interconnect the cover layer and the backing layer. As an additional but not required feature are according to EP 0 071 212 B1 particles of inert rock particles, such as sand, gravel or the like, are present in the holding fibers. The holding fibers needled through the particle layer keep the cover layer and the underlayer spaced apart and are bonded to the cover layer and the underlayer.

As nonwovens are particularly solid staple fiber webs, but also filament, meltblown and spun nonwovens in question, which are usually additionally solidify. As possible solidification methods for nonwovens mechanical, thermal and chemical solidification are known. If, in the case of mechanical consolidation, the fibers are held together purely mechanically by swirling of the individual fibers, by intermeshing fiber bundles or by sewing in additional threads, thermal or chemical methods can be used to bond adhesive (with binder) or cohesive (binder-free) fiber-fiber Achieve bonds. With suitable formulation and process control, these can be limited exclusively or at least predominantly to fiber nodes, so that a stable, three-dimensional network is formed while maintaining the loose, open structure in the nonwoven.

Nonwovens have proven to be particularly advantageous, which are solidified in particular by overmilling with separate threads or by intermeshing.

Such solidified nonwovens are produced, for example, on stitchbonding machines of the type "Malimo" from Karl Mayer, formerly Malimo, and are available, inter alia, from Hoftex Group AG. A Malivlies is characterized in that a cross-fiber fleece is solidified by the formation of stitches of fibers of the fleece.

As a carrier, a fleece of the Kunit or Multiknit type can furthermore be used. A Kunitvlies is characterized in that it results from the processing of a longitudinally oriented nonwoven fabric to a fabric having on one side mesh and on the other mesh webs or Polfaser-folds, but has neither threads nor prefabricated fabrics. Such a nonwoven fabric has also been produced for some time, for example, on stitchbonding machines of the type "Malimo" from Karl Mayer. Another characteristic feature of this nonwoven is that it can absorb high tensile forces in the longitudinal direction as longitudinal fiber fleece. A Multiknitvlies is compared to the Kunitvlies characterized in that the fleece by the piercing on both sides with needles on both the top and on the bottom undergoes a solidification. As a starting product for a multi-cut usually serve a or two produced by the Kunit process unilaterally intermeshed non-woven fabric fibers. In the final product, both nonwoven topsheets are formed into a closed surface by fiber meshing and bonded together by nearly vertical fibers. The additional applicability of further pierceable fabrics and / or spreadable media is given. Finally, nonwoven webs are suitable as a precursor to form a carrier according to the invention and an inventive adhesive tape. A stitchbonded web is formed from a nonwoven material having a plurality of seams running parallel to one another. These seams are created by sewing or stitching of continuous textile threads. For this type of nonwoven stitching machines of the type "Malimo" Karl Mayer known.

Needle fleeces are also particularly suitable. In the case of the needled nonwoven, a batt becomes a sheet by means of barbed needles. By alternating piercing and pulling the needles, the material is solidified on a needle bar, whereby the individual fibers devour into a solid sheet. The number and embodiment of the needling points (needle shape, penetration depth, double-sided needling) determine the strength and strength of the fiber structures, which are generally light, air permeable and elastic.

Also particularly advantageous is a staple fiber fleece which is preconsolidated by mechanical processing in the first step or which is a wet fleece which has been hydrodynamically laid, wherein between 2% by weight and 50% by weight of the fibers of the fleece are melt fibers, in particular between 5 Wt .-% and 40 wt .-% of the fibers of the nonwoven. Such a nonwoven fabric is characterized in that the fibers are wet-laid or, for example, a staple fiber fleece is pre-consolidated by the formation of loops of fibers of the fleece by needling, suturing, air and / or water jet machining. In a second step, the heat-setting takes place, wherein the strength of the nonwoven fabric is further increased by the melting or melting of the melt fibers.

For the use according to the invention of nonwovens, the adhesive bonding of mechanically pre-consolidated or wet-laid nonwovens is of particular interest, and this can be achieved by adding binder in solid, liquid, foamed or pasty form. Basic forms of administration are variously possible, for example solid binders as powders for trickling, as a foil or as a grid or in the form of binding fibers. Liquid binders are dissolved in water or organic solvents or can be applied as a dispersion. Bonding dispersions are predominantly selected for adhesive bonding: thermosetting plastics in the form of phenolic or melamine resin dispersions, elastomers as dispersions of natural or synthetic rubbers or mostly dispersions of thermoplastics such as acrylates, vinyl acetates, polyurethanes, styrene-butadiene systems, PVC and the like. and their copolymers. In the normal case, these are anionic or non-ionogenically stabilized dispersions, but in special cases, cationic dispersions may also be advantageous.

The type of binder application can be carried out according to the prior art and can be read, for example, in standard works of the coating or nonwoven technology such as "nonwovens" (Georg Thieme Verlag, Stuttgart, 1982) or "Textiltechnik-Nonwoven Production" (Employer Group Gesamttextil, Eschborn, 1996).

For adequate adhesive bonding of the nonwoven backing, it is generally necessary to add binders of the order of 1% to 50%, in particular 3% to 20%, based on the weight of the nonwoven fabric.

The addition of the binder can be carried out already during the nonwoven production, during the mechanical pre-consolidation or else in a separate process step, wherein this can be carried out in-line or off-line. After the binder has been added, a condition has to be temporarily created for the binder in which it becomes adhesive and adhesively bonds the fibers - this can be achieved during drying, for example, by dispersions, but also by heating, whereby further variations can be achieved by surface or partial pressure application are. The activation of the binder can be done in known drying channels, with a suitable choice of binder but also by means of infrared radiation, UV radiation, ultrasound, high-frequency radiation or the like. For the later end use, it makes sense, but not absolutely necessary, for the binder to have lost its stickiness after the end of the nonwoven production process. It is advantageous that volatile components such as fiber adjuvants are removed by thermal treatment and thus a fleece with favorable Foggingwerten, so that when using a low fogging adhesive tape can be produced with particularly favorable Foggingwerten, as well as the carrier thus shows a very low Foggingwert.

Advantageously and at least in regions, the carrier has a surface ground on one or both sides smooth, preferably in each case a surface smoothed over the entire surface. The smoothed surface may be chinted, as for example in the EP 1 448 744 A1 is explained. In this way, the repellency of dirt is improved.

As starting materials for the carrier are in particular (chemical) fibers (staple fiber or continuous filament) of synthetic polymers, also called synthetic fibers of polyester such as polyethylene terephthalate, polyamide, polyimide, aramid, polyolefin, polyacrylonitrile or glass, (chemistry) fibers of natural polymers such cellulosic fibers (viscose, modal, lyocell, cupro, acetate, triacetate, cellulon), such as gum fibers, such as vegetable protein fibers, and / or such as animal protein fibers and / or natural fibers of cotton, sisal, flax, silk, hemp, linen, coconut or wool , However, the present invention is not limited to the materials mentioned, but it can, recognizable to those skilled to work without having to be inventive, a variety of other fibers for the production of the web can be used. Furthermore, yarns made from the specified raw materials are also suitable.

For woven or laid single yarns can be made from a mixed yarn, so have synthetic and natural ingredients. As a rule, however, the warp threads and the weft threads are each of a type-specific design. The warp threads and / or the weft threads can each consist only of synthetic threads or threads of natural raw materials.

Polyester or glass, more preferably polyester, is preferably used as the material for the carrier because of the excellent aging resistance and the excellent resistance to chemicals and equipment such as oil, gasoline, antifreeze and the like. In addition, polyesters and glass have the advantages of resulting in a very wear-resistant and temperature-resistant support, which is of particular importance for the particular purpose of bundling cables in automobiles and, for example, in the engine compartment.

Advantageously, the basis weight of the textile carrier between 30 g / m ² and 300 g / m ^{2 is} more advantageously between 50 g / m ² and 200 g / m ² , particularly advantageously between 60 g / m ² and 150 g / m ² , completely particularly advantageous between 70 g / m ² and 100 g / m ² .

According to a particularly advantageous embodiment of the invention, the carrier used is a woven fabric or a fleece made of polyester, which has a weight per unit area of between 60 g / m ² and 150 g / m ² .

According to the invention, it is possible that the gel layer contains no flame retardant or, if it contains flame retardants, less than 10 wt .-% flame retardant. It has been found that with such levels of flame retardant properties of the gel layer are not or hardly affected. The properties of the gel layer, which can also be regarded as the carrier layer of the adhesive tape, have a significant influence on the performance of the adhesive tape. Therefore, according to the invention, the lower the levels of flame retardants in the gel layer, the more preferred they are. Preferably, the gel layer contains no or less than 8 wt .-%, more preferably no or less than 6 wt .-%, in particular no or less than 3 wt .-%, for example, no or less than 1 wt .-% flame retardant.

Most preferably, the gel layer is free of flame retardants. "Free from" in this context does not necessarily mean "free from" in the hard mathematical sense, but is to be understood as "free from added flame retardants". Contents of flame retardants in the range of omnivorous concentration or technically unavoidable resulting from the preparation of the gel layer amounts are considered according to the invention with respect to the feature "free of flame retardant" as irrelevant.

The adhesive tape according to the invention comprises a first and a second outer pressure-sensitive adhesive layer. The term "outer pressure-sensitive adhesive layer" is understood in the sense that the respective pressure-sensitive adhesive layer can develop an adhesive effect directed outward, that is to say onto a substrate not belonging to the adhesive tape. This assumes that it is not covered on its outside with another layer. A release liner, as it is usually used to protect the adhesive surfaces of an adhesive tape, according to the invention, however, is not considered as part of the adhesive tape. This means that the "outer pressure-sensitive adhesive layer" is to be designated as such, even if it is covered with a release liner.

A pressure-sensitive adhesive or a pressure-sensitive adhesive is understood in this document to mean, as is generally customary in the art, a substance which, especially at room temperature, is permanently tacky and tacky. It is characteristic of a pressure-sensitive adhesive that it can be applied by pressure to a substrate and adhere there, whereby the pressure to be applied and the duration of this pressure are not further defined. In some cases, depending on the exact nature of the pressure-sensitive adhesive, the temperature and humidity, and the substrate, the application of short-term, minimum pressure, which does not go beyond a light touch for a brief moment to achieve the adhesion effect, is sufficient in others Cases may also require a longer-term exposure time of high pressure.

Pressure-sensitive adhesives have special, characteristic viscoelastic properties which lead to permanent tackiness and adhesiveness.

Characteristic of them is that when they are mechanically deformed, it comes both to viscous flow processes as well as to build elastic restoring forces. Both processes are in a certain ratio with respect to their respective proportions, depending on the exact composition, the structure and the degree of crosslinking of the pressure-sensitive adhesive to be considered as well as on the speed and duration of the deformation and on the temperature.

The proportional viscous flow is necessary to achieve adhesion. Only the viscous portions, caused by macromolecules with relatively high mobility, allow a good wetting and a good flow onto the substrate to be bonded. A high proportion of viscous flow leads to a high pressure tack (also referred to as tack or surface tackiness) and thus often also to a high bond strength. Strongly crosslinked systems, crystalline or glassy solidified polymers are usually not or at least only slightly tacky due to the lack of flowable components.

The proportional elastic restoring forces are necessary to achieve cohesion. They are caused for example by very long-chained and strongly entangled as well as by physically or chemically crosslinked macromolecules and allow the transmission of forces acting on an adhesive bond forces. They result in an adhesive bond being able to withstand a sustained load acting on it, for example in the form of a permanent shearing load, to a sufficient extent over a relatively long period of time.

For a more detailed description and quantification of the degree of elastic and viscous component as well as the ratio of the components to one another, the variables storage modulus (G ') and loss modulus (G ") which can be determined by means of dynamic mechanical analysis (DMA) can be used elastic proportion, G "is a measure of the viscous portion of a substance. Both quantities depend on the deformation frequency and the temperature.

The sizes can be determined with the help of a rheometer. The material to be examined is exposed to a sinusoidal oscillating shear stress in a plate-and-plate arrangement, for example. In shear stress controlled devices, the deformation as a function of time and the time lag of this deformation are compared with the introduction of the shear stress measured. This time offset is referred to as the phase angle δ.

The storage modulus G 'is defined as follows: G' = (т /))) · cos (δ) (т = shear stress, ү = deformation, δ = phase angle = phase shift between shear stress vector and deformation vector). The definition of the loss modulus G "is: G" = (т / y) · sin (δ) (т = shear stress, = = deformation, δ = phase angle = phase shift between shear stress vector and deformation vector).

A substance is generally considered to be pressure-sensitive and is defined as tacky, if at room temperature, here by definition at 23 ° C, in the deformation frequency range of 10 ° to 10 ¹ rad / sec, G 'at least partially in the range of 10 ^third is up to 10 ⁷ Pa and when G for "at least partly in this range. i.e. in part, that at least a portion of the G 'curve is within the window formed by the deformation of the frequency range including 10 ° up to and including 10 ¹ rad / sec (abscissa) and the range of G 'values from 10 ³ to 10 ⁷ Pa inclusive (ordinate) is spanned, and if at least a portion of the G "curve lies within this window accordingly.

The adhesive tape according to the invention comprises a first and a second outer pressure-sensitive adhesive layer. So it's a double-sided tape. The second outer PSA layer may be identical to the first, but it may also differ from this.

The outer pressure-sensitive adhesive layers preferably contain at least one polymer selected from the group consisting of poly (meth) acrylates, natural rubber, synthetic rubbers, silicones, polyurethanes and mixtures of two or more of the polymers listed above. Particularly preferably, the outer pressure-sensitive adhesive layer contains at least one poly (meth) acrylate. In particular, the outer pressure-sensitive adhesive layer contains no further polymers except one or more poly (meth) acrylates.

"Poly (meth) acrylates" - in accordance with the general understanding - understood polymers that are accessible by free-radical polymerization of acrylic and / or methylacrylic monomers and optionally other copolymerizable monomers. The term "poly (meth) acrylate" according to the invention comprises both polymers based on acrylic acid and derivatives thereof as well as those based on acrylic acid and methacrylic acid and their derivatives as well as those based on methacrylic acid and derivatives thereof, wherein the polymers are always acrylic acid esters, methacrylates or mixtures of acrylic and methacrylic acid esters. The poly (meth) acrylates of the outer pressure-sensitive adhesive layer preferably have an average molar mass M _w of at most 600,000 g / mol.

(vgl. T.G. Fox, Bull. Am. Phys. Soc. 1 (1956) 123) ein T_G-Wert für das Polymer von ≤ 25 °C ergibt. Ein solcher Wert ist besonders vorteilhaft für Haftklebemassen, die im Wesentlichen bei Raumtemperatur eingesetzt werden.The monomers of the poly (meth) acrylates of the outer pressure-sensitive adhesive layer and their quantitative composition are preferably selected such that, according to the so-called Fox equation (G1) $$\frac{1}{{\text{T}}_{\text{G}}}={\displaystyle \underset{\text{n}}{\Sigma }\frac{{\text{w}}_{\text{n}}}{{\text{T}}_{\text{G}\text{, n}}}}$$

(see. TG Fox, Bull. Phys. Soc. 1 (1956) 123) gives a T _G value for the polymer of ≤25 ° C. Such a value is particularly advantageous for pressure-sensitive adhesives which are used essentially at room temperature.

In the equation G1, n represents the number of runs via the monomers used, w _n the mass fraction of the respective monomer n (% by weight) and T _{G, n} the respective glass transition temperature of the homopolymer from the respective monomers n in Kelvin.

1. a) Acrylsäureester und/oder Methacrylsäureester der Formel (I) CH₂ = C(R^I)(COOR^II) (I), worin R^I = H oder CH₃ und R^II ein Alkylrest mit 1 bis 30 C-Atomen, stärker bevorzugt mit 4 bis 14 C-Atomen, besonders bevorzugt mit 4 bis 9 C-Atomen, ist;
2. b) olefinisch ungesättigte Monomere mit funktionellen Gruppen, die eine Reaktivität mit Vernetzersubstanzen aufweisen;
3. c) optional weitere olefinisch ungesättigte Monomere, die mit den Monomeren (a) und (b) copolymerisierbar sind.

Preferably, the outer pressure-sensitive adhesive layer contains one or more poly (meth) acrylate (s), which can be attributed to the following monomer composition:

1. a) acrylic acid esters and / or methacrylic acid esters of the formula (I) CH ₂ = C (R ^I ) (COOR ^II ) (I), wherein R ^I = H or CH ₃ and R ^II is an alkyl group having 1 to 30 carbon atoms, more is preferably having from 4 to 14 carbon atoms, particularly preferably having 4 to 9 carbon atoms;
2. b) olefinically unsaturated monomers having functional groups which have a reactivity with crosslinker substances;
3. c) optionally further olefinically unsaturated monomers which are copolymerizable with the monomers (a) and (b).

Examples of the substituent R "are methyl acrylate, methyl methacrylate, ethyl acrylate, n-butyl acrylate, n-butyl methacrylate, n-pentyl acrylate, n-hexyl acrylate, n-heptyl acrylate, n-octyl acrylate, n-octyl methacrylate, n-nonyl acrylate, lauryl acrylate, stearyl acrylate, behenyl acrylate and their branched isomers, such as, for example, isobutyl acrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, isooctyl acrylate, isooctyl methacrylate, R '' particularly preferably represents a methyl, an n-butyl and a 2-ethylhexyl group, in particular an n-butyl and a 2-ethylhexyl group.

The monomers b) are preferably olefinically unsaturated monomers having functional groups which can undergo a reaction with epoxide groups. Particularly preferably, the monomers b) each contain at least one functional group selected from the group consisting of hydroxyl, carboxy, sulfonic acid and phosphonic acid groups, acid anhydride functions, epoxide groups and substituted or unsubstituted amino groups.

In particular, the monomers b) are selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, aconitic acid, dimethylacrylic acid, β-acryloyloxypropionic acid, trichloroacrylic acid, vinylacetic acid, vinylphosphonic acid, maleic anhydride, 2-hydroxyethyl acrylate, 3-hydroxypropyl acrylate, 2- Hydroxyethyl methacrylate, 3-hydroxypropyl methacrylate, 6-hydroxyhexyl methacrylate, allyl alcohol, glycidyl acrylate and glycidyl methacrylate. Very particular preference is given to the monomers b) acrylic acid and / or methacrylic acid, in particular acrylic acid.

Suitable monomers c) are in principle all vinylically functionalized compounds which are copolymerizable with the monomers a) and the monomers b). With the selection and amount of the monomers c), properties of the pressure-sensitive adhesive of the invention can be advantageously regulated.

The monomers c) are particularly preferably selected from the group consisting of methyl acrylate, ethyl acrylate, n-propyl acrylate, methyl methacrylate, ethyl methacrylate, benzyl acrylate, benzyl methacrylate, sec-butyl acrylate, tert-butyl acrylate, phenyl acrylate, phenyl methacrylate, isobornyl acrylate, isobornyl methacrylate, tert-butylphenyl acrylate, tert-butylphenyl methacrylate, dodecyl methacrylate, isodecyl acrylate, lauryl acrylate, n-undecyl acrylate, stearyl acrylate, tridecyl acrylate, behenyl acrylate, cyclohexyl methacrylate, cyclopentyl methacrylate, phenoxyethyl acrylate, 2-butoxyethyl methacrylate, 2-butoxyethyl acrylate, 3,3,5-trimethylcyclohexyl acrylate, 3,5-dimethyladamantyl acrylate, 4- Cumyl phenyl methacrylate, cyanoethyl acrylate, cyanoethyl methacrylate, 4-biphenyl acrylate, 4-biphenyl methacrylate, 2-naphthyl acrylate, 2-naphthyl methacrylate, tetrahydrofurfuryl acrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, 3-methoxyacrylic acid methyl ester, 3-methox ybutyl acrylate, phenoxyethyl acrylate, phenoxy ethyl methacrylate, 2-phenoxyethyl methacrylate, butyl diglycol methacrylate, ethylene glycol acrylate, ethylene glycol monomethyl acrylate, methoxy polyethylene glycol methacrylate 350, methoxy polyethylene glycol methacrylate 500, propylene glycol monomethacrylate, butoxy diethylene glycol methacrylate, ethoxytriethylene glycol methacrylate, octafluoropentyl acrylate, octafluoropentyl methacrylate, 2,2,2-trifluoroethyl methacrylate, 1,1, 1,3,3,3-hexafluoroisopropyl acrylate, 1,1,1,3,3,3-hexafluoroisopropyl methacrylate, 2,2,3,3,3-pentafluoropropyl methacrylate, 2,2,3,4,4,4-hexafluorobutyl methacrylate, 2,2,3,3,4,4,4-heptafluorobutyl acrylate, 2,2,3,3,4,4,4-heptafluorobutyl methacrylate, 2,2,3,3,4,4,5,5,6, 6,7,7,8,8,8-pentadecafluorooctyl methacrylate, dimethylaminopropylacrylamide, dimethylaminopropylmethacrylamide, N- (1-methyl-undecyl) acrylamide, N- (n-butoxymethyl) acrylamide, N- (butoxymethyl) methacrylamide, N- (ethoxymethyl) acrylamide, N- (n-octadecyl) acrylamide, N, N-dialkyl-substituted amides, esp N, N-dimethylacrylamide, N, N-dimethylmethacrylamide, N-benzylacrylamide, N-isopropylacrylamide, N-tert-butylacrylamide, N-tert-octylacrylamide, N-methylolacrylamide, N-methylolmethacrylamide; further acrylonitrile, methacrylonitrile; Vinyl ethers such as vinyl methyl ether, ethyl vinyl ether, vinyl isobutyl ether; Vinyl esters such as vinyl acetate; Vinyl chloride, vinyl halides, vinylidene halides, vinylpyridine, 4-vinylpyridine, N-vinylphthalimide, N-vinyllactam, N-vinylpyrrolidone, styrene, α- and p-methylstyrene, α-butylstyrene, 4-n-butylstyrene, 4-n-decylstyrene, 3 , 4-dimethoxystyrene, 2-polystyrene ethyl methacrylate (MW of 4000 to 13000 g / mol) and poly (methyl methacrylate) ethyl methacrylate (Mw of 2000 to 8000 g / mol). In particular, the monomer c) is methyl acrylate.

The monomers c) can advantageously also be chosen such that they contain functional groups which promote radiation-chemical crosslinking (for example by electron beams or UV). Suitable copolymerizable photoinitiators are, for example, benzoin acrylate and acrylate-functionalized benzophenone derivatives. Monomers which promote electron beam crosslinking are, for example, tetrahydrofurfuryl acrylate, N-tert-butylacrylamide and allyl acrylate.

If the outer pressure-sensitive adhesive layer contains a plurality of poly (meth) acrylates, it is particularly preferable for all the poly (meth) acrylates of the outer pressure-sensitive adhesive layer to be due to the monomer composition described above. In particular, all the poly (meth) acrylates of the outer pressure-sensitive adhesive layer are due to a monomer composition consisting of acrylic acid, n-butyl acrylate, 2-ethylhexyl acrylate and methyl acrylate.

Most preferably, the poly (meth) acrylate or all the poly (meth) acrylates of the outer pressure-sensitive adhesive layer are based on the following monomer composition: acrylic acid 1-10% by weight methyl acrylate 3-20% by weight 2-ethylhexyl acrylate 25-50% by weight, n-butyl acrylate 25-50% by weight, wherein the proportions of the monomers add up to 100 wt .-%.

The poly (meth) acrylates can be prepared by radical polymerization of the monomers in solvents, in particular in solvents having a boiling range of from 50 to 150.degree. C., preferably from 60 to 120.degree. C., using the usual amounts of polymerization initiators, generally at 0, 01 to 5, in particular at 0.1 to 2 wt .-% (based on the total weight of the monomers) are prepared.

In principle, all known to the expert, customary initiators are. Examples of radical sources are peroxides, hydroperoxides and azo compounds, for example dibenzoyl peroxide, cumene hydroperoxide, cyclohexanone peroxide, di-t-butyl peroxide, cyclohexylsulfonyl acetyl peroxide, diisopropyl percarbonate, t-butyl peroctoate, benzpinacol. In a very preferred procedure, the radical initiator used is 2,2'-azobis (2-methylbutyronitrile) or 2,2'-azobis (2-methylpropionitrile) (2,2'-azobisisobutyronitrile; AIBN).

Suitable solvents for the preparation of the poly (meth) acrylates are alcohols such as methanol, ethanol, n- and iso-propanol, n- and iso-butanol, preferably isopropanol and / or isobutanol, and hydrocarbons such as toluene and in particular gasoline having a boiling range of 60 up to 120 ° C in question. It is also possible to use ketones, such as, preferably, acetone, methyl ethyl ketone, methyl isobutyl ketone and esters, such as ethyl acetate, and mixtures of solvents of the type mentioned, with mixtures containing isopropanol, in particular in amounts of from 2 to 15% by weight, preferably from 3 to 10% by weight. , based on the solvent mixture used, are preferred.

Preferably, the proportion of the total of polymers selected from the group consisting of poly (meth) acrylates, natural rubber, synthetic rubbers, silicones, polyurethanes and mixtures of two or more of the polymers listed above on the outer pressure-sensitive adhesive layer 35 to 90 wt .-%, stronger preferably 40 to 75 wt .-%, in particular 45 to 68 wt .-%, most preferably 50 to 62 wt .-%, for example 52 to 60 wt .-%, each based on the total weight of the outer PSA layer. The proportion of the total of poly (meth) acrylates in the outer pressure-sensitive adhesive layer is particularly preferably 35 to 90% by weight, more preferably 40 to 75% by weight, in particular 45 to 68% by weight, very particularly preferably 50 to 62 Wt .-%, for example 52 to 60 wt .-%, each based on the total weight of the outer pressure-sensitive adhesive layer.

The double-sided adhesive tape of the invention further comprises at least one flame-retardant adhesive layer. This is preferably also a pressure-sensitive adhesive layer. For the at least one flame-retardant adhesive layer, the information regarding components and properties described above for the outer pressure-sensitive adhesive layer applies. Reference is therefore made to avoid repetition. Incidentally, flame-retardant adhesive layer and outer pressure-sensitive adhesive layer may otherwise be constituted the same or different except for the flame retardant contained in the case of the flame-retardant adhesive layer. Also, in the case where two flame-retardant adhesive layers are used with a carrier, the two flame-retardant adhesive layers may be the same or different.

According to the invention, the flame-retardant PSA layer contains at least 10% by weight of flame retardant. The flame-retardant PSA layer preferably comprises from 10 to 35% by weight of flame retardant, more preferably from 12 to 30% by weight of flame retardant, in particular from 14 to 28% by weight. Flame retardant, for example 17 to 26 wt .-% flame retardant, each based on the total weight of the flame-retardant PSA layer. It is therefore provided according to the invention that the flame retardancy properties of the adhesive tape are substantially, preferably completely determined by the flame retardant contained in the flame-retardant PSA layer or in the flame-retardant PSA layers. It has been found that it is sufficient to provide the flame retardant pressure sensitive adhesive layer (s) with flame retardant to achieve adequate flame retardancy. Advantageously, this makes it possible to keep the release layer largely or completely free from being influenced by added flame retardant. Many, in particular mechanical, properties of the adhesive tape are fully realized in this way and are not mitigated in their manifestation by flame retardant additives.

Preferably, the gel layer contains less than 8 wt .-%, more preferably less than 6 wt .-%, in particular less than 3 wt .-%, for example less than 1 wt .-%, most preferably no flame retardant, and the flame retardant PSA layer contains 10 to 35 wt .-% flame retardants, more preferably 12 to 30 wt .-% flame retardants, in particular 14 to 28 wt .-% flame retardants, for example 17 to 26 wt .-% flame retardants, each based on the total weight of the relevant layer.

Flame retardants which can be used in the adhesive tape of the invention include, for example, alumina hydrates, zinc borates, ammonium phosphates, antimony oxide, chloroparaffins, polychlorinated biphenyls, hexabromobenzene, polybrominated diphenyl ethers; organic phosphates, phosphites and phosphonates, for example tritolyl phosphate and tert-butylphenyl diphenyl phosphate; Phosphinic acid salts and diphosphinic acid salts, for example, aluminum trisdiethylphosphinate, aluminumtrismethylethylphosphinate, aluminumtrisethylbutylphosphinate, titanylbisdiethylphosphinate, titanium tetrakisdiethylphosphinate, titanylbismethylethylphosphinate, titanium tetrakismethylethylphosphinate, titanylbisethylbutylphosphinate, titanium tetrakisethylbutylphosphinate, zinc bisdiethylphosphinate, zinc bismethylethylphosphinate, zinc bisethylbutylphosphinate; and halogenated organic phosphorus compounds such as tris (2,3-dibromopropyl) phosphate, tris (2-bromo-4-methylphenyl) phosphate and tris (2-chloroisopropyl) phosphate. Halogen-free flame retardants are preferred according to the invention. The flame retardants which can be used according to the invention are therefore preferably selected from the group consisting of aluminum oxide hydrates, zinc borates, ammonium polyphosphates, antimony oxide; organic phosphates, phosphites and phosphonates; Phosphinic salts and diphosphinic salts and mixtures of two or more of the flame retardants listed above. The flame retardants which can be used according to the invention are particularly preferably selected from the group consisting of ammonium polyphosphates and also phosphinic and diphosphinic acid salts. In particular, the flame retardant comprises aluminum diethylphosphinate. In a specific embodiment, the adhesive tape according to the invention contains no further flame retardants except Aluminiumdiethylphosphinat.

The flame-retardant PSA layer may contain, in addition to one or more polymers and one or more flame retardants, further constituents, for example anti-aging agents, plasticizers, crosslinkers and / or promoters. These substances are collectively referred to below as "excipients". In one embodiment of the invention, the outer pressure-sensitive adhesive layer contains at least one tackifying resin selected from the group consisting of pinene, indene and rosin resins and their disproportionated, hydrogenated, polymerized, esterified derivatives and salts; aliphatic and aromatic hydrocarbon resins, terpene resins, terpene-phenolic resins, and mixtures of two or more of the tackifying resins listed above. Of the hydrocarbon resins, all (soluble) resins compatible with the corresponding poly (meth) acrylate can be used; in particular, reference is made to all aliphatic, aromatic, alkylaromatic hydrocarbon resins, hydrocarbon resins based on pure monomers, hydrogenated hydrocarbon resins, functional hydrocarbon resins, and natural resins, in particular C. ₅ to C ₉ hydrocarbon resins. More preferably, the outer pressure-sensitive adhesive layer contains at least one tackifying resin selected from terpene-phenolic resins and C ₅ -C ₉ -hydrocarbon resins. In particular, the outer pressure-sensitive adhesive layer contains a terpene-phenolic resin.

Preferably, the outer pressure-sensitive adhesive layer contains 5 to 45% by weight, more preferably 10 to 38% by weight, especially 13 to 35% by weight, most preferably 15 to 30% by weight of tackifying resin (s ).

In one embodiment of the invention, the outer pressure-sensitive adhesive layer contains 40 to 75% by weight Poly (meth) acrylate, 10 to 38% by weight tackifying resin, 10 to 35% by weight Flame retardants, and 0 to 5% by weight excipients wherein the parts by weight add up to 100% by weight.

In particular, the outer pressure-sensitive adhesive layer contains 45 to 68% by weight Polymethacrylate having the following monomer composition: acrylic acid 1-10% by weight methyl acrylate 3-20% by weight 2-ethylhexyl acrylate 25-50% by weight, n-butyl acrylate 25-50% by weight, wherein the proportions of the monomers add up to 100 wt .-%; 13 to 35% by weight Terpene phenol resin; From 12 to 30% by weight Flame retardants; and 0 to 5% by weight Excipients.

The adhesive tape of the invention may comprise further layers, as are customary in the construction of adhesive tapes, for example primer layers, barrier layers, getter layers, reinforcing layers, etc.

The layer structure of the adhesive tape according to the invention can in principle be produced by all suitable technologies, for example by coating or laminating. The adhesion between the individual layers can be improved by subjecting one or both surfaces of the gel layer and / or the surface of the flame-retardant adhesive layer facing the gel layer or the outer pressure-sensitive adhesive layer and / or the surface of the outer pressure-sensitive adhesive layer facing the flame-retardant adhesive layer to a corona or plasma treatment becomes. Likewise, a primer can be applied between the release layer and the flame-retardant adhesive layer and / or the flame-retardant adhesive layer and the outer pressure-sensitive adhesive layer, if appropriate also between these and further layers.

The outer pressure-sensitive adhesive layer may be covered with a release liner to protect it from the adhesion of dust and other environmental contaminants. There are all known liner systems in question. Liner serve to cover a pressure-sensitive adhesive layer until it is applied in the application, a liner is thus an aid that must be disposed of after its removal from the PSA layer. The same applies to a release film, which is a special case of a liner insofar as the release coating is applied to a film. A liner is generally and also not considered in the context of the present invention as part of the adhesive tape, but rather only as an aid. Carriers are fundamentally different from liners since carriers are a permanent component of an adhesive tape or label. Carriers are always firmly bonded to PSA layer (directly or through a primer, also called a primer). The same applies to the distinction between a release film and a film adhesive tape carrier.

Liners are usually release papers (papers with one or two-sided silicone coating) or release films (often polyester, polypropylene or polyethylene films with silicone coating). In accordance with the invention, however, other separation systems or release coatings may also be considered.

An example of a sleeve with enveloped airbag according to the invention is in the 1 to 5 shown. It shows 1 a sleeve 1 for wrapping an airbag 2, the in 2 is shown in rolled-up form. The sleeve 1 has an adhesive tape on one edge 2 on.

3 shows the airbag 3 wrapped in the sleeve 1 , The sleeve 1 is by means of adhesive tape 2 locked. The tape 2 thus fixes the sleeve 1 around the airbag 3 , The sleeve 1 can completely surround the airbag or, as in 3 shown the ends of the airbag 3 set free. 4 is a side view of the in 3 shown from the sleeve 1 enveloped airbags 1 , in the direction of the arrow IV of 3 seen. In 4 is good to see how the tape 2 the sleeve 1 around the airbag 3 fixed around by the overlapping area of both ends of the sleeve 1 by means of adhesive tape 2 is closed. At the tape 2 it is a double-sided adhesive tape, which has a pressure-sensitive adhesive layer on both sides, so that the adhesive tape is mounted on the inside of the outer end of the sleeve 1 and thus not visible from the outside.

The structure of an adhesive tape according to the invention 2 shows 5 , The tape 2 consists of at least three layers 4 . 5 . 6 , In the 5 with reference number 5 designated layer is a flame retardant layer. This flame retardant layer 5 represents the flame retardant properties of the entire tape 2 ready. In the simplest version is the flame-retardant layer 5 a flame-retardant pressure-sensitive adhesive layer containing at least 10% by weight of a flame retardant. Likewise it is possible that the flame retardant layer 5 itself is composed of three layers, namely two flame-retardant adhesive layers with an intermediate gel layer.

On both sides of the flame retardant layer 5 each is a pressure-sensitive adhesive layer 4 . 6 applied. These two layers 4 . 6 , which may consist of the same PSA or consist of different PSAs, must have no flame retardant properties. They are designed to ensure good adhesion to the sleeve material. The flame retardant properties ensures the flame retardant layer 5 ,

Examples

Various double-sided adhesive tapes were produced.

Pressure-sensitive adhesive A was prepared as follows:

A conventional 2 L glass reactor for free-radical polymerizations was charged with 12 g of acrylic acid, 20 g of methyl acrylate, 174 g of n-butyl acrylate, 194 g of 2-ethylhexyl acrylate and 300 g of acetone / isopropanol (99: 1). After passing nitrogen gas through with stirring for 45 minutes, the reactor was heated to 58 ° C. and 0.2 g of 2,2'-azobisisobutyronitrile (AIBN, Vazo 64®, DuPont) was added. Subsequently, the outer heating bath was heated to 75 ° C and the reaction was carried out constantly at this external temperature. After 1 h of reaction time, 0.2 g Vazo 64 was again added. After 3 and 6 h each was diluted with 150 g of an acetone / isopropanol mixture (99/1). To reduce the residual initiators, 0.4 g of di- (4-tert-butylcyclohexyl) peroxydicarbonate (Perkadox 16®, Akzo Nobel) were added after 8 and 10 h. The reaction was stopped after 22 h reaction time and cooled to room temperature.

The determination of the molecular weight according to Test A gave a Mw = 1,100,000 g / mol with a polydispersity M _W / M _n = 7.3.

The adhesive was then freed of solvent under heat and in vacuo and blended in a kneader with 30 wt .-% (based on the polymer) terpene phenolic resin and 20 wt .-% of Aluminiumdiethylphosphinat as a flame retardant.

The mass thus obtained was coated as a hotmelt through a die onto a siliconized release paper (Laufenberg company) (coat application 50 g / m ² or 100 g / m ² ). The PSAs were crosslinked with 60 kGy and 200 kV ES.

The pressure-sensitive adhesive B is identical to the pressure-sensitive adhesive A, only the proportion of flame retardant is 0 wt .-%; So there is no flame retardant added ..

Various adhesive tapes having the parameters shown in Table 1 were prepared and subjected to a burning test. The fire behavior is measured according to FMVSS 302 (horizontal sample). For FMVSS 302, the pressure-sensitive adhesive coating is up. Table 1: Adhesive tape assemblies Examples 1 2 3 4 5 6 50 g / m ² adhesive B 50 g / m ² adhesive B 50 g / m ² adhesive B 50 g / m ² adhesive B 50 g / m ² FR adhesive A 100 g / m ² adhesive A 50 g / m ² adhesive A 100 g / m ² Adhesive A 50 g / m ² adhesive B 25μm flame retardant PET carrier 25μm PET carrier 50 g / m ² adhesive B 50 g / m ² adhesive B 50 g / m ² adhesive B 50 g / m ² adhesive A 50 g / m ² adhesive B

The results are included in Table 2. Worst and best results were determined as the average of three tests. Table 2: Results example 1 2 3 Test method substrates Condition FMVSS 302 fleece material RT SE > 80 mm / min SE Peel Adhesion 180 ° at 300 mm / min Pet plate RT - 10.2 N / cm Pet plate 105 ° C / 400hrs reconditioning RT / 4hrs - 13.4 N / cm Pet plate -40 ° C / 400hrs reconditioning RT / 4hrs - 11.8 N / cm fleece material RT <1 N / cm 8.18 N / cm * example 4 5 6 Test method substrates Condition FMVSS 302 fleece material RT > 150 mm / min > 80 mm / min <80mm / min Peel Adhesion 180 ° at 300 mm / min Pet plate RT Pet plate 105 ° C / 400hrs reconditioning RT / 4hrs Pet plate -40 ° C / 400 hrs reconditioning RT / 4 hrs fleece material RT RT: room temperature

180 ° bond strength steel - fleece

The determination of the bond strength on the PET plate was carried out at a test climate of 23 ° C +/- 1 ° C temperature (room temperature) and 50% +/- 5% rel. Humidity or when stored in the specified time at the specified temperature. The samples were cut to a width of 20 mm and glued to a PET plate or to a commercially available fleece. The PET plate was taken before the measurement cleaned and conditioned. For this purpose, the plate was first wiped with isopropanol and then left for 2 hours in the air, so that the solvent could evaporate.

The side of the laminar composite facing away from the test substrate was then covered with a 36 μm-etched PET film, which prevented the sample from stretching during the measurement. After that, the test pattern was rolled up on the ground. For this purpose, the adhesive tape was rolled over with a 2 kg roller five times back and forth at a winding speed of 10 m / min. Immediately after curling, the bond strength was measured with a Zwick tensile tester.

The measurement results are given in N / cm and are averaged out of three measurements.

The measurement results show that a single-layered adhesive tape consisting of a flame-retardant adhesive layer (Example 1) meets the FMVSS 302 standard and is self-extinguishing.

Example 2 shows that a three-layer adhesive tape comprising three adhesive layers can not achieve the object according to the invention if the middle adhesive layer, which is provided with 20% by weight of flame retardant, and the outer adhesive layers have a basis weight of 50 g / m ² ,

Example 3 shows that a three-layer adhesive tape composed of three adhesive layers can achieve the object according to the invention if the middle adhesive layer, which is provided with 20% by weight of flame retardant, has a basis weight of 100 g / m ² , while the outer adhesive layers have a surface weight of 50 g / m ^{2 are} applied (ratio of the surface weights of the flame-retardant layer to the sum of the basis weights of the two outer pressure-sensitive adhesive layers at 1: 1).

The measurement results show that a single-layer adhesive tape consisting of adhesive layer (Example 4), which is not flame-retardant, does not meet the FMVSS 302 standard.

Example 5 corresponds almost to Example 2, wherein a 25 micron thick PET film is used as the middle layer. Due to the lack of equipment of the adhesives with flame retardant fails this tape. This is very remarkable in that the carrier itself is equipped with flame retardants and still no extinction is observed.

Example 6 shows that a five-layer adhesive tape of four layers of adhesive material can achieve the object according to the invention if a 25 μm thick PET film is used as the central support, to which adhesive layer layers having a basis weight of 50 g / m ^{2 are} applied directly above and below which are equipped with 20 wt .-% flame retardants. Adhesive layers having a weight per unit area of 50 g / m ² are in turn applied directly to the middle adhesive layers at the top and bottom, with the adhesives not being rendered flame-retardant.

Surprisingly, despite the additional PET carrier, this adhesive tape is also self-extinguishing, because the ratio of the basis weights of the flame-retardant layers to the sum of the basis weights of the two outer pressure-sensitive adhesive layers is 1: 1 in the preferred ratio.

This is very remarkable compared to Example 5, in that the carrier is not itself equipped with flame retardants.

QUOTES INCLUDE IN THE DESCRIPTION

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

Cited patent literature

• EP 16179112 [0017]
• EP 0071212 B1 [0028]
• EP 1448744 A1 [0039]

Cited non-patent literature

• Standard ISO 3795 [0006]
• T. G. Fox, Bull. Phys. Soc. 1 (1956) 123) [0060]

Claims (11)

Use of an adhesive tape (2) for fixing a sleeve (1) surrounding an airbag (3), characterized in that the adhesive tape (2) is flame-retardant. Use after Claim 1 , characterized in that the adhesive tape (2) is formed carrier-free. Use after Claim 1 , characterized in that the adhesive tape (2) has at least one carrier which is coated on at least one side, preferably on both sides, with a flame-retardant adhesive. Use after Claim 3 , characterized in that the carrier is a stabilizing scrim Use after Claim 3 or 4 , characterized in that the flame-retardant adhesive applied on at least one side contains at least 10% by weight of flame retardant, based on the total weight of the flame-retardant adhesive layer. Use after at least one of Claims 1 to 5 , characterized in that the adhesive tape (2) has an outer pressure-sensitive adhesive layer (4, 6) on at least one side, the outer pressure-sensitive adhesive layer containing no or less than 10% by weight of flame retardant. Double-sided adhesive tape (2), in particular for use according to at least one of Claims 1 to 6 wherein the adhesive tape (2) consists of at least three layers (4, 5, 6), characterized in that the at least three layers (4, 5, 6) are the following layers: a) a first outer pressure-sensitive adhesive layer ( 4) b) a flame-retardant layer (5) comprising at least one flame-retardant pressure-sensitive adhesive layer containing at least 10% by weight, preferably from 15 to 35% by weight of a flame retardant, and c) a second outer pressure-sensitive adhesive layer (6). Double-sided adhesive tape (2) after Claim 7 characterized in that the flame retardant layer b) (5) further comprises a further flame retardant pressure sensitive adhesive layer containing at least 10%, preferably 15 to 35% by weight of a flame retardant and a stabilizing gel layer, wherein the stabilizing gel layer between the two flame retardant PSA layers is arranged. Double-sided adhesive tape (2) after Claim 7 or 8th , characterized in that the ratio of the total weight of the flame-retardant layer (5) to the total weight of the two outer pressure-sensitive adhesive layers (4, 6) is at least 0.7: 1, preferably at least 0.95: 1, more preferably at least 1: 1. Double-sided adhesive tape (2) after Claim 9 characterized in that the two outer pressure-sensitive adhesive layers (4, 6) each have substantially the same weight and the flame-retardant layer (5) has an overall weight that is substantially twice the total weight of each of the two outer pressure-sensitive adhesive layers (4, 6). Sleeve (1), surrounding an airbag (3), characterized in that the sleeve (1) with a double-sided adhesive tape (2) according to one of Claims 7 to 10 closed is.

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