Compositions – Fire retarding – Intumescent
Reexamination Certificate
2002-07-22
2004-05-11
Thexton, Matthew A. (Department: 1714)
Compositions
Fire retarding
Intumescent
C524S099000, C524S108000, C524S136000, C524S141000
Reexamination Certificate
active
06733697
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of enhancing the flame retardancy of flame retardants, the enhanced (or activated) flame retardants and their applications. The activated flame retardants provide enhanced flame retardancy to virtually a limitless number and types of applications. For example, the activated flame retardants provide improved flame retardancy in polymers (including thermosetting, thermoplastic, polymer matrices, mixtures of polymers, copolymer, terpolymers, etc . . . ) coatings, paints, films, resins, binders, and fibers.
BACKGROUND OF THE INVENTION
Several solutions are known in the art to reduce or eliminate the combustibility of polymers. Intumescent materials have been used for over forty years in industry. One of the first commercial intumescent agents used to provide fire protection by means of char formation was para nitro analine ortho sulfonic acid ammonium salt. Currently, the more common intumescent agents are generally constituted by the polymer of the system and at least three main additives: an essentially phosphorus-containing additive whose purpose is of forming, during the combustion, an impermeable, semi-solid vitreous layer, essentially constituted by polyphosphoric acid, and of activating the process of formation of intumescence; a second additive, containing nitrogen, which performs the functions of a foaming agent; and a third, carbon-containing additive, which acts as a carbon donor to allow an insulating cellular carbonaceous layer (“char”) to be formed between the polymer and the flame. Phosphates that release phosphoric acid at high temperature are frequently employed.
Examples of intumescent formulations of this type include those reported by the following patents: U.S. Pat. No. 3,810,862 (Phillips Petroleum Co.) based on melamine, pentaerythritol and ammonium polyphosphate; U.S. Pat. No. 4,727,102 (Vamp S.r.l.), based on melamine cyanurate, a hydroxyalkyl derivative of isocyanuric acid and ammonium polyphosphate; U.S. Pat. No. 6,015,510 (E.I. du Pont de Nemours and Company) based on melamine pyrophosphate and other conventional components; and by published patent application WO 85/05626 (Plascoat U.K. Limited), on the basis of various phosphorus and nitrogen compounds among which, in particular, a combination of melamine phosphate pentaerthritol and ammonium polyphosphate has to be cited.
In more recent formulations, together with the use of an organic or inorganic phosphorus compound a nitrogen-containing organic compound was used, generally consisting of an amino plastic resin obtained by condensation of urea, melamine or dicyandiamide with formaldehyde.
Examples of formulations containing two additives are those reported in the following patents: U.S. Pat. No. 4,504,610 (Montedison S.p.A.) based on oligomeric derivatives of 1,3,5-triazine and ammonium polyphosphate; and European Pat. No. 14463 (Montedison S.p.A.) based on organic compounds selected from among benzylguanamine and reaction products between aldehydes and several nitrogenious cyclic compounds, in particular benzylguanamine-formaldehyde copolymers, and ammonium polyphosphate.
Self-extinguishing compositions can also be obtained by using single-component additives, which contain in their organic molecule both nitrogen and phosphorus atoms, as disclosed in U.S. Pat. No. 4,201,705 (Borg-Wagner Corp.).
These intumescent flame retardant systems endow the polymers, which contain them, with the property of forming a carbonaceous residue when they undergo a fire, or are exposed to high temperatures. The present invention provides a method for of improving present and future nitrogenous phosphorus and/or sulfonate flame retardants. The activated flame retardants of the present invention provide one or more of the following advantages: improved char yield (includes faster generation of char and/or higher quantity of char), char density, self-extinguishing characteristics, thermal insulation (upon activation), and/or lower smoke emissions to the composition.
SUMMARY OF THE INVENTION
The present invention provides a method of forming an activated nitrogenous phosphate and/or nitrogenous sulfonate flame retardant, having enhanced flame retardancy, by forming the nitrogenous phosphate and/or sulfonate component in the presence of a char forming catalyst and/or a phase transfer catalyst.
A further aspect of the present invention is an activated flame retardant comprising at least one nitrogenous phosphorus and/or sulfonate and at least one activator. An activator includes a char forming catalyst and/or a phase transfer catalyst.
Another aspect of the present invention provide an article having improved flame retardancy by the incorporation of an activated flame retardant.
DETAILED DESCRIPTION OF THE INVENTION
In this application, the following terms will be understood to have the following meaning:
“activated flame retardant” means a flame retardant that provides improved flame retardancy, for example as measured by the Char Yield Value test discussed herein, with the incorporation of at least one activator, char forming catalyst and/or phase transfer catalyst, of the present invention than without an activator. Preferably, the activator is present in the activated flame retardant in a minor amount, for example less than 5 wt. %, or even less than 2 wt. % and preferably between 0.01 to 1.8 wt. %;
“halogen-free” means essentially free of halogens [i.e., contains less than 0.25 percent (preferably, less than 0.1 percent; more preferably, less than 0.01 percent)] by weight halogen calculated on an elemental basis as Cl, F, etc., based on the total weight of the flame retardant;
“hetero” refers to a component or compound comprising in addition to carbon and hydrogen atoms another type of atom (preferably oxygen, nitrogen, or sulfur atoms);
“metal-free” means essentially free of metals [i.e., contains less than 0.25 percent (preferably, less than 0.1 percent; more preferably, less than 0.01 percent)] by weight metal calculated on an elemental basis, based on the total weight of the flame retardant; and
“intumescent” refers to a material which expands upon heating above about 100° C., preferably above 190° C. or even 250° C., although the temperature at which a particular intumescent material intumesces is dependent on the composition of that material.
The activated flame retardants of the present invention may be used in the same applications as “uunactivated” flame retardants are presently used or would be used. The employment of the activated flame retardants impart enhanced flame retardancy. Specifically, the activated flame retardant imparts improved char yield (includes faster generation of char and/or higher quantity of char), char density, self-extinguishing characteristics, thermal insulation (upon activation), and/or lower smoke emissions to the composition. In addition, the preferred flame retardant of the present invention are those that are halogen-free and/or metal-free which impart known benefits to systems beyond the flame retardancy benefits.
As a consequence, the activated flame retardants may be employed to impart an increased flame retardancy or employed in lesser (loadings) amounts to impart comparable flame retardancy. The type and loading levels of the activated flame retardant in a particular system is dependent on the specific design criteria. The loading levels of the activated flame retardant may be for example as low as 1, 5, or 8 wt. % and as high as 20, 30 or even 50 wt. %, relative to the total weight of the system.
Typical systems in which the activated flame retardant may be employed include compositions comprising synthetic materials and/or polymers including epoxies, polyamides (including nylon 6,6, and nylon 4,6), polyesters, polycarbonates, polyacrylates, polyethers, polyolefins, polyurethanes, derivatives of these polymers, copolymers, mixtures of these polymers, and mixtures comprising these polymers with other components. Suitable thermoplastic polymers that may be incorporated into such compositions
Izrailev Leonid
Rhodes Michael S.
Rhodes Philip S
Tuerack Jason
Pillsbury & Winthrop LLP
Thexton Matthew A.
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