Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Dixon, Merrick (Department: 1774)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S370000, C428S390000, C428S423100, C428S921000
The present invention relates to a fire-retarding composition, comprising an intumescent agent, intended to be applied to a substrate, for example to yarns or textile structures, so as to render them more fire-resistant. The present invention will be more particularly described in relation to the fire-retarding of yarns and textile structures, and the non-inflammability requirements of such yarns and textile structures.
It is already known, for example from U.S. Pat. No. 3,934,066, to apply, for example by impregnation, an intumescent agent to a porous support and to incorporate or apply the said fire-retarded support to combustible substrates so as to render them non-inflammable. The intumescent agent comprises water-soluble or water-dispersible components, especially a thermodegradable strong-acid compound, for example phosphoric acid, and a polyhydric carbon compound, for example pentaerythritol.
Quite a detailed description of the operation and of the composition of such systems is given in the article in the French journal entitled “Plastiques Modernes, Dossiers Additifs [
Modern Plastics, Additives Section
], August 1994 ” and the article published in “Flame Retardants '94”. However, and as emphasized in this document, the actual application of these agents, compared with the wide choice possible, has hitherto been very limited.
In general, such intumescent agents are also known in combination with plastics. For example, U.S. Pat. No. 4,256,786 describes a fire-retarding composition for the impregnation of a plastic-based foam, or its combination with a textile layer, especially a polyurethane foam with a cotton fabric. The compositions are obtained by preparing an aqueous paste containing activated charcoal, an ammonium polyphosphate, a pentaerythritol and a binder, which may be an acrylic resin. Such resins are used as a minor part of the fire-retarding composition, other components being incorporated (for example activated carbon, esterified copolymer of maleic anhydride and of styrene, CMC), which may increase the non-inflammability of the fire-retarding composition. Moreover, the compositions described in that document cannot be used for fire-retarding products which will be exposed to the weather, since they exhibit moisture-uptake problems.
Moreover, U.S. Pat. No.5,185,103 describes an intumescent composition for fire-retarding electrical cables, comprising an organic polymer, ammonium polyphosphate (APP) and an (alkyl carbonate) polyol. The organic polymer is insoluble in water and is generally thermoplastic, for example polyethylene, polypropylene, EVA and polyesterurethanes. The composition is obtained by simply mixing the various components at a sufficient temperature for the organic polymer to be in the liquid state (generally between 125°-300° C. [sic], preferably between 150°-200° C. [sic]). However, these compositions have all proved to be lacking in terms of non-inflammability.
In the description and claims, and in accordance with the definitions given in the above articles, the terms and expressions indicated below have the following meanings:
“a thermodegradable strong-acid compound” is a compound which releases a strong acid, either by itself or in situ from a precursor, at high temperature, i.e. between approximately 100° C. and approximately 250° C.;
“a polyhydric carbon compound” is a compound generally chosen from the various classes of carbohydrates, and which has a relatively high amount of carbon and many hydroxyl sites;
“a blowing or expansion agent” is an agent separate from the strong-acid compound and the polyhydric carbon compound, which releases non-inflammable gases, such as CO
, during its thermal degradation and which contribute [sic] to the intumescent effect by forming an expanded carbon structure; these compounds are generally amines and amides.
The technical problem that the Applicant set out to solve is to obtain a fire-retarding composition comprising a binding fraction and an intumescent agent, while keeping or improving the properties of the intumescent agent without correspondingly impairing the basic properties of the binding fraction, for example its thermal-bonding behavior and/or its resistance to water uptake, which would allow it to be applied to substrates, such as specialty yarns or textile structures, especially specialty fabrics, for example in the form of blinds, and to obtain improved fire resistance in these products.
The Applicant has therefore studied such compositions and has discovered that the solution to the problem posed above resides in the need to start with a binding fraction which itself has minimal non-inflammability, in combination with a certain weight ratio of the thermodegradable strong-acid compound to the polyhydric carbon compound, thereby making it possible to provide flexibility with regard to the amount and the composition of the intumescent agent to be used.
Consequently, one subject of the present invention relates to a halogen-free fire-retarding plastic composition, which can be applied to a substrate, comprising a binding fraction, which binds the said composition, and an intumescent agent consisting of a thermodegradable strong-acid compound and a polyhydric carbon compound. The composition is more particularly characterized in that the binding fraction as such has a limited oxygen index (LOI) of at least 25% and the intumescent agent essentially consists of the said strong-acid compound and the said polyhydric carbon compound, the solids content of the composition having a weight ratio of the said strong-acid compound to the said polyhydric carbon compound of between 1.5 and 2, and preferably 1.85.
In fact, the Applicant has discovered that this ratio in combination with the limited oxygen index of the binding fraction was important for ensuring that a finished product is obtained, for example a fire-retarded yarn and textile fabric, having the necessary characteristics for manufacturing blinds for example. In particular, it has been discovered that, if the ratio goes below the value of 1.5, the products fire-retarded with this composition had too high a water uptake and were difficult to process. Moreover, it has been discovered that if the ratio exceeds the value of 2, difficulties are encountered in coating the composition, for example on yarns, and the intumescence becomes very insufficient.
The present invention therefore makes it possible to dispense with any other fire-retarding agent, especially a toxic fire-retarding agent, such as melamine.
Another subject of the present invention is a fire-resistant composite yarn comprising a core made of a halogen-free material and a sheath made of a plastic, the composition of the said plastic being identical to the fire-retarding composition according to the definition given above. This fire-resistant composite yarn may be preferably obtained by coating the core with such a fire-retarding composition. The core may be of diverse nature, for example a yarn made of an inorganic or organic material, of natural or synthetic origin, such as glass, polyester, polyamide, polypropylene or polyethylene, and contain no halogen or halogen compound.
In a preferred embodiment of this subject, the fire-resistant yarn has a limited oxygen index, measured according to the NF G 07128 standard, of between approximately 40% and approximately 50%, preferably of 45%, and an intumescent expansion factor of between approximately 30% and approximately 60%, preferably of 50%.
A third subject of the present invention is a textile structure, consisting of an assembly or entanglement of the fire-resistant yarns defined above.
A fourth subject of the present invention is a fire-retarded composite textile structure, comprising a halogen-free fibrous support and at least one layer or film coating the fibrous support, the said layer or the said film being identical to the fire-retarding composition defined above. Textile structures of this type may be, for example, specialty fabrics, nonwoven structures and knitte
Oliff & Berridg,e PLC
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