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Approach for achieving flame retardancy while retaining physical properties in a compatible polymer matrixRelated Patent Categories: Synthetic Resins Or Natural Rubbers -- Part Of The Class 520 Series, Natural Rubber Compositions Having Nonreactive Materials (dnrm) Other Than: Carbon, Silicon Dioxide, Glass Titanium Dioxide, Water, Hydrocarbon, Halohydrocarbon, Ethylenically Unsaturated Reactant Admixed With A Preformed Reaction Product Derived From: (a) At Least One Polycarboxylic Acid, Ester, Or Anhydride; (b) At Least One Polyhydroxy Compound; And (c) At Least One Fatty Acid Glycerol Ester, Or A Fatty Acid Or Salt Derived From A Naturally Occurring Glyceride, Tall Oil, Or A Tall Oil Fatty Acid, Solid Polymer Derived From Sulfur-containing ReactantApproach for achieving flame retardancy while retaining physical properties in a compatible polymer matrix description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20080064833, Approach for achieving flame retardancy while retaining physical properties in a compatible polymer matrix. Brief Patent Description - Full Patent Description - Patent Application Claims
ORIGIN OF INVENTION [0001] The invention described herein was made by employees of the United States Government and may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefore. BACKGROUND [0002] Flame retardant plastics and additives are a 2.2 billion dollar market. Flame retardant plastics and additives are used in electronic devices, mattresses and cushions, and fabrics, including fabrics used in pajamas, blankets, and tents (Chemical and Engineering News, Dec. 4, 2000, Vol. 78, No. 49, pp. 21-31). [0003] Heat stabilizers, primarily used in polyvinylchloride pipes, are a 1.8 billion dollar market. Lead and mixed metals such as cadmium/zinc are the most common heat stabilizers. But these have the disadvantage that lead and some other metals are known to carry health risks (Id.). [0004] The most commonly used flame retardants are bromine-, chlorine-, or antimony-containing compounds. An example is brominated polystyrene. Brominated polystyrene is added to polystyrene at an appropriate level to create flame retardant properties. The addition of brominated polystyrene, however, degrades the physical properties of the polystyrene. Halogenated polymers also pose environmental problems. They are believed to release polybrominated dioxins and polybrominated dibenzofurans when incinerated (Id.). Other typical flame retardant additives include halogenated biphenyls, antimony oxide, ammonium polyphosphate, inorganic hydroxides, and organophosphates. [0005] Polybenzoxazoles (PBOs) are one type of flame retardant polymer. Polybenzoxazoles are quite rigid and form a char in heat. The char can seal and protect other flammable materials from fire or heat. (So, Y. H. 2000. Prog. Polym. Sci. 25:137.) [0006] Polyhydroxyamides (PHAs) are polymers that cyclize in heat to form PBOs. (Yoo, E.-S. et al. 2003. High Performance Polymers 15:519.) [0007] New flame-retardant and heat-stable polymer compositions are needed. Preferably the polymer compositions can retain the range of properties available in polymers that are flammable and heat labile. SUMMARY [0008] The invention is based on the discovery that incorporating even relatively small amounts of polyhydroxyamide (PHA) and related polymers into polymer blends with larger amounts of other polymers that are flammable or unstable in heat (e.g., nylon) produces blends that are surprisingly flame resistant and resistant to thermal degradation, but that otherwise substantially retain the physical characteristics of the flammable or unstable polymers in the blend. Blends containing more PHA than flammable polymer are even more flame-resistant and durable against thermal degradation than the blends containing low amounts of PHA, and are also useful. [0009] The structure of one type of PHA is shown below as formula 5 Upon heating, the hydroxyl and carbonyl groups of polymer 5 cyclize with loss of water to form a polybenzoxazole (PBO), shown in formula 9. The reaction absorbs energy and helps to resist or extinguish flames. The PBO that is formed also is flame retardant and can form a char upon exposure to flame that seals other materials from the flame. [0010] A PHA of the form of compound 10 is also flame retardant and forms a forms a flame retardant polybisbenzoxazole 11 upon heating. [0011] Thus, one embodiment of the invention provides a polymer blend comprising: [0012] (a) one or more flammable polymers; and [0013] (b) a flame-resistant polymer having repeating units of formula 1 or 2 wherein [0014] one of R.sup.1 and R.sup.2 together with one of R.sup.3 and R.sup.4 form a polymer backbone group where each Y is independently O or S; and Z is a bivalent radical of from 1 to 100 atoms; [0015] the other of R.sup.1 and R.sup.2 and the other of R.sup.3 and R.sup.4 are each --OR.sup.6, where each R.sup.6 is independently H, (C.sub.1-C.sub.6)alkyl, (C.sub.1-C.sub.6)alkylcarbonyl, phenyl, --S(O)(O)(OR.sup.7), --P(O)(OR.sup.7)(OR.sup.7), --P(O)(N(R.sup.7).sub.2)(OR.sup.7), --P(O)(N(R.sup.7).sub.2)(N(R.sup.7).sub.2), --P(O) (R.sup.7C).sub.2, --P(O)(OR.sup.7)(R.sup.7), --P(O)(N(R.sup.7).sub.2)(R.sup.7), or --Si(R).sub.3; [0016] each R.sup.5 is independently H, halo, (C.sub.1-C.sub.4)alkyl, phenyl, phenyl(C.sub.1-C.sub.4)alkyl, hydroxy, (C.sub.1-C.sub.4)alkoxy, (C.sub.1-C.sub.4)alkylcarbonyl, (C.sub.1-C.sub.4)alkylcarbonyloxy, phenyloxy, --OS(O)(O)(OR.sup.7), or --OP(O)(OR.sup.7)(OR.sup.7); [0017] each R.sup.7 is independently H, (C.sub.1-C.sub.6)alkyl, or phenyl; [0018] X is a bivalent radical of from 1-100 atoms, and p is 0 or 1; [0019] any alkyl or phenyl can optionally be substituted with one or more halo, hydroxy, nitro, merc-apto, cyano, (C.sub.1-C.sub.6)alkoxy, trifluoromethyl, oxo, --N(R.sup.8).sub.2, or --OC(O)R.sup.8, wherein each R.sup.8 is independently H or (C.sub.1-C.sub.6)alkyl; [0020] the repeating units of formula 1 or 2 of (b) comprise 0.1 to 65% by weight of the polymer blend; [0021] the polymer blend is flame resistant; Continue reading about Approach for achieving flame retardancy while retaining physical properties in a compatible polymer matrix... 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