EP0447605A1 - Fire barrier composed of non-woven fibre structures - Google Patents

Abstract

A fire barrier composed of non-woven material made of partially graphited polyacrylonitrile fibres is a component of a flat laminated structure, the non-woven material being consolidated with high-energy water jets and having a surface weight of 40 to 100 g/m<2> and its fibres not containing any impregnation.

Description

The invention relates to a textile flame barrier as part of a flat multilayer structure. Known flame barriers are flame-retardant fabrics that are used in flame-resistant clothing, on interior fittings in the passenger area of air, land and sea vehicles, on vehicle fittings, such as Tarpaulins or engine compartment linings, in upholstery material, in textile interior fittings, in pillows and mattresses.

The term flame barrier means that it prevents a flame from passing through a visible material into the interior of any of the above items. This property is explained in detail in Melliand Textile Reports 6/1987, 396-401.

It has been proposed to use a lightweight nonwoven fabric made from flame retardant fibers. (Melliand textile reports 6/1987, 396-401). Numerous organic and inorganic, flame-retardant fibers are mentioned in the publication and their limiting oxygen index (hereinafter referred to as LOI value) is listed. This index determines the flammability of plastics in accordance with ISO standard 4589 "Plastics - Determination of the Flammability by the Oxygen Index" and can also be used with certain restrictions on textiles, provided they consist of organic fibers. Effective flame retardant behavior can be expected in our atmosphere with LOI values above about 27.

US Pat. No. 4,748,065 discloses a flame retardant nonwoven that is impregnated with carbon particles adsorbing chemical vapors. It is used for fireproof clothing. The nonwoven fibers consist of at least 90% aramid staple fibers, the nonwoven has a basis weight of 35 to 70 g / m², and the fibers are strengthened by two water jet treatments, once with a jet pressure of about 1400 kPa, then with jet pressures between 10,000 and 11,000 kPa. The 10 to 50% by weight of absorbent carbon particles present as impregnation serve exclusively for the sorption of harmful gases and have no influence on the flammability.

This flame-retardant nonwoven fabric of the prior art is essentially made up of fibers which can still be melted and is therefore destroyed when exposed to direct flame; it is therefore not a flame barrier. The flame test according to ISO 8191-1 and -2 is not passed.

• a) Flächengewicht nicht über 100 g/m² bei einer Dicke von maximal 1,8 mm;
• b) Textiler Fall und Tragekomfort;
• c) Flammbarrierewirkung gemäß ISO 8191-1 und -2;
• d) Resistenz gegen glimmende, daraufliegende Körper;
• e) in Verbindung mit einer Haftmassenbeschichtung leicht kaschierbar;
• f) Festigkeit von mindestens 70 N/5 cm Breite in mindestens einer Richtung;
• g) Erhalt der Wirkung als Flammbarriere auch nach dem Aufbügeln mittels Haftmasse auf einen Oberstoff.

The object of the present invention is to circumvent the disadvantages mentioned and to create a flame barrier made of nonwoven fabric which has the combinations of the following properties:

• a) basis weight not exceeding 100 g / m² with a maximum thickness of 1.8 mm;
• b) Textile case and comfort;
• c) flame barrier effect according to ISO 8191-1 and -2;
• d) resistance to glowing, lying bodies;
• e) easy to laminate in conjunction with an adhesive coating;
• f) strength of at least 70 N / 5 cm width in at least one direction;
• g) Preservation of the effect as a flame barrier even after ironing on an outer fabric by means of adhesive.

Weights should be possible down to 40 g / m². Experience has shown that this value roughly represents the lower limit, down to which an even fiber density sufficient for flame protection is still guaranteed. Furthermore, lower basis weights would result in increased surface abrasion and reduced tear resistance. Particular attention must be paid to high strength when the flame barrier is to be used in heavily used upholstery. Strengths in all surface directions above 70 N / 5 cm are required there.

Basis weights over 100 g / m² should be avoided for economic reasons and because of the disadvantageously increasing rigidity of the flame barrier.

The solution to the above problem consists in a textile flame barrier with the characterizing features of the first claim. Advantageous configurations are shown in the subclaims.

The water jets act on the fibers at a pressure of approx. 10,000 kPa. It is also possible to continuously and continuously increase the pressure up to 14,000 kPa.

Partially graphitized polyacrylonitrile fibers are used as fibers for the flame-retardant nonwoven fabric according to the invention. Partially graphitized means that the fibers are only graphitized to the extent that they can still be rolled up. Fully graphite fibers cannot be used because they cannot be processed using carding machines. The LOI value of the fibers used should be between 40 and 65. This value is to be regarded as a measure of the graphitization; the lower the graphitization, the lower the LOI value and vice versa.

As will be shown in the examples, basis weights in the range of 70 g / m 2 and below can only be achieved with these fibers, without the effect of the nonwoven as a flame barrier decreasing. When using aramid fibers mixed with cellulose fibers or 100%, the nonwoven according to fire test according to ISO norm 8191-1 and -2 no longer has a flame retardant effect. These fibers, which are otherwise also used in flame-retardant nonwovens, are therefore not suitable for the present invention, which requires low basis weights.

It is also important for the present invention that all fibers do not have to have any impregnation in order to achieve the object. The use of often toxicologically questionable flame retardant and / or physically effective absorption layers is completely unnecessary with the present invention.

Nonwovens manufactured in this way are already sufficient for many areas of application where flame protection is required, e.g. as flame barriers for down pillows that are said to be resistant to smoldering cigarettes.

For the majority of uses, e.g. for upholstered furniture subject to higher mechanical loads, however, the strength of such a nonwoven is not yet satisfactory.

It can therefore be provided with reinforcing threads that run in the warp / weft direction. Using known sewing techniques, it is readily possible to achieve minimum strengths of 70 N per 5 cm if one shoots in 4 to 24 threads per inch in the warp direction and 4 to 15 threads per centimeter in the weft direction. Instead of a full weft binding, a short weft binding can also be used. These reinforcing threads are contained in the nonwoven with a weight fraction of 12 to 60 g / m². Although such strengths are lower than those of a 200 g / m² fabric of the prior art, they are completely sufficient for all purposes.

The claimed partially graphitized polyacrylonitrile fibers have LOI values of at least 40. It is obvious that materials with these LOI values are also used as materials for the warp and weft threads.

Surprisingly, this is usually not necessary; reinforcing threads below the LOI value 40 are also suitable without the flame protection being impaired. Materials for the reinforcement threads are e.g. Aramids, polyamideimide, aromatic polyimide, highly cross-linked phenolic polymers or thermally stabilized polyacrylonitrile. The expert will be able to make the selection easily on the basis of numerous literature describing these materials. The high costs of these special filaments represent a serious disadvantage.

It would have been expected that reinforcing threads made of the much cheaper thermoplastic materials with LOI values below 27, e.g. made of polyester or polyamide, can be completely excluded.

However, it has been shown completely surprisingly that within the scope of the present invention it is in fact possible in many cases to choose thermoplastic materials with an LOI value even below 27 for the reinforcement threads associated with a binding direction, without the flame-retardant effect of the nonwoven fabric or its strength disadvantageously affected by fire.

From the point of view of the overall strength of the flame barrier according to the invention, it has proven to be the most sensible to specifically choose the warp threads from the cheaper thermoplastic materials mentioned. These melt away when the nonwoven fabric is flamed; However, the favorable fact that the remaining entire fiber composite of the nonwoven fabric retains the properties of a flame barrier was unpredictable.

In many cases, the flat multilayer structure, which carries the flame barrier on the outside, should be provided on the visible side with decorative material which itself does not need to have any flame-retardant properties. For this purpose, the surface of the nonwoven flame barrier facing the outside can be provided with a thermoplastic adhesive that binds the decorative material. This can be designed in the form of a point, line or area. It is known to increase the flammability of the adhesive by means of special additives, e.g. reduce red phosphorus with phosphates or bromine salts or Al (OH) ₃. However, these additives are problematic because of the often considerable toxicity of their reaction products when exposed to fire and when they are disposed of, or they involve additional production costs.

Unexpectedly, it has now been found that with the flame barrier according to the invention, pure thermoplastic adhesive compositions can be used on the outside without the flame-retardant additives mentioned, the protective properties of the flame barriers not being lost. This even applies in the same way to the majority of the bonds between the nonwoven fabric and the underlying fabric to be protected. Only in areas of application where there is an extreme risk of fire in a highly flammable environment, e.g. for bonnet covers, the flame-retardant additives alone cannot be completely dispensed with for the internal adhesive.

For applications where high isotropic strength is required, for example for upholstery, the nonwoven fabric according to the invention can be reinforced in the weight range from 30 to 50 g / m² by doubling or laminate binding.

A light-weight, flame-retardant nonwoven is coated with thermoplastic or reactive adhesive, which does not have to contain any flame-retardant additives, by known methods, e.g. with paste printing, powder point or scatter coating. A second, also 30 to 50 g / m² heavy, flame retardant nonwoven is laminated in a continuous press with the first nonwoven. This achieves a higher isotropy in the strength and in the extensibility, and in the case of warp / weft-reinforced nonwovens, the weft threads are better retained in the laminate.

The following examples are intended to describe the subject matter of the invention in more detail. In particular, it should be shown that when using partially graphitized polyacrylonitrile fibers with the technique of water jet needling, lightweight nonwovens with high flame resistance are obtained.

Example 1:

A nonwoven fabric of 70 g / m², made of partially graphitized polyacrylonitrile staple fibers with an LOI value of 60 and a titer of 1.7 dtex in an isotropic fiber orientation, is consolidated in two stages with columnar water jets. There are 5 nozzle bars in each stage, the holes of which have a diameter of 120 µm and are arranged at intervals of 0.6 mm. In the first stage, the top of the fleece is consolidated with jet pressure increasing from nozzle bar to nozzle bar, starting at 25 bar and ending at 140 bar.

In the second stage, the nonwoven fabric is consolidated on its underside, with the pressures from nozzle bar to nozzle bar being staggered from 80 bar to 140 bar.

In both stages, the nonwoven is transported on a 100 mesh screen belt in order to obtain a flat structure with a closed surface.

The nonwoven is then soaked with a hydro- and oleophobic effect, commercially available fluorocarbon resin so that 2% resin remain on the fabric.

An adhesive of copolyamide with a melting range of 112 to 116 ° C in an amount of 25 g / m² is printed on the finished nonwoven semi-material, on the surface that later turns away from the outside. The adhesive contains a commercially available flame retardant based on a halogen-free organic phosphorus compound.

The finished surface material serves as a high-temperature-resistant, non-meltable, heat- and sound-insulating insulation nonwoven for sound insulation parts in the field of internal combustion engines. It is highly deformable, hydro- and oleophobic and, thanks to its permanent deformation and the adhesive coating, can be easily laminated with foams, nonwovens, felts, fiberglass and rock wool.

Example 2:

In the same way as in Example 1, a nonwoven fabric is produced with a basis weight of 50 g / m 2, consisting of cross-laid, hydroentangled carbon fibers. The nonwoven is made with a magazine weft machine with nonwoven liner with polyethylene terephthalate warp yarn (5 g / m², 50 dtex f 22) and a weft yarn based on aramid (11 g / m², 22 dtex f 100) with a distance of 3 mm in the warp and one Distance of 25 mm reinforced in the shot.

The warp / weft reinforced nonwoven fabric produced in this way can be used in duvets and pillows. The actual upholstery material consists of an outer material made of meltable, flame-retardant polyester, an inlay made of the same material and a down filling. This construction alone does not resist a lit cigarette; the down is charred. However, if the nonwoven fabric according to the invention is sewn to the ticking fabric, the passage of the flame is prevented and the down remains undamaged.

Example 3:

A nonwoven fabric of 70 g / m 2 made of 100% partially charred polyacrylonitrile fibers as in Example 1, with a titer of 1.7 dtex, is laid down with a card and cross layer and then hydroentangled in accordance with the conditions of Example 1. 15 g / m² of a copolyamide adhesive with a melting range of 112 to 116 ° C. are printed on this nonwoven fabric, but in contrast to example 1 it contains no flame retardant.

This material is ironed with an upholstery made of flame-retardant polyester fibers and placed on a combustible polyurethane foam 75 mm thick. The flame test according to ISO standard 8191-1 and -2 shows that the foam does not start to burn when the above-mentioned laminate is present.

A much thinner fabric of the same structure with the same basis weight does not prevent the flame from passing through.

Example 4:

• a) 100 g Aramidfaser, 1,7 dtex;
• b) 35 % Aramidfaser 1,7 dtex, 65 % flammhemmend ausgerüstete Zellulosefaser, 1,7 dtex.

Beide Vliesstoffe zeigen im Brandtest nach ISO Norm 8191-1 und -2 keine flammhemmende Wirkung: Der sich unter bzw. hinter dem Vliesstoff befindende Schaumstoff brennt ab.Example 3 is repeated with the following two fiber mixtures:

• a) 100 g aramid fiber, 1.7 dtex;
• b) 35% aramid fiber 1.7 dtex, 65% flame retardant cellulose fiber, 1.7 dtex.

In the fire test according to ISO Norm 8191-1 and -2, both nonwovens show no flame-retardant effect: the foam located under or behind the nonwoven burns off.

Example 5:

A nonwoven fabric of 35 g / m 2 made of 100% partially graphitized polyacrylonitrile fibers as in Example 1, with a titer of 1.7 dtex, is laid down with a card and cross layer and then hydroentangled in accordance with the conditions of Example 1. 50 g / m² of a copolyamide adhesive with a melting range of 112 ° C. to 116 ° C. are printed on this nonwoven fabric, but in contrast to example 1 it contains no flame retardant.

This material is laminated with a nonwoven fabric of 50 g / m² made of 100% partially charred polyacrylonitrile fibers as in Example 1 in a continuous press at a fixing temperature of 120 ° C. The strength is approximately the same in all levels - directions; it is 75 Nm. The composite can be stretched equally far in all directions.

Claims (5)

Flame barrier made of nonwoven fabric as part of a flat multilayer structure, the nonwoven fabric consisting of infusible fibers, solidified with high-energy water jets and having a basis weight of 40 to 100 g / m² and a thickness of at most 1.8 mm, characterized in that it consists of partially graphitized Polyacrylonitrile fibers with an LOI value of at least 40 exist and that these fibers have no impregnation. Flame barrier according to claim 1, characterized in that the nonwoven additionally contains reinforcing threads running in a warp / weft arrangement in an amount of 12 to 60 g / m², with 4 to 24 threads per inch in the warp direction and 4 to 15 threads per centimeter in the weft direction are embedded and the nonwoven finished in this way has a minimum strength of 70 N / 5cm. Flame barrier according to claim 2, characterized in that the reinforcing warp threads have an LOI value below 27 and consist of thermoplastic material. Flame barrier according to one of the preceding claims, characterized in that at least one of its surfaces is provided with a thermoplastic adhesive which contains no flame-retardant additives. Flame barrier according to claim 4, characterized in that the nonwoven fabric with a basis weight of 30 to 50 g / m² is doubled or laminated with a second nonwoven fabric of 30 to 50 g / m², which has the features of claims 1, 2 or 3, wherein the adhesive is between the two nonwovens.