Patent Application
20150210848
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1. Field of Invention
The compositions described herein are generally related to flame retardant engineering plastics that exhibit excellent processing characteristics and thermal and mechanical properties. The invention also relates to methods for preparing such compositions and articles of manufacture prepared from these flame retardant compositions.
2. Description of Related Art
Commodity engineering plastics such as, for example, polyesters, polyamides, polycarbonates, polyacrylates, polystyrenes and the like are used in a variety of applications. Most engineering plastics are not inherently fire resistant and consequently specific additives such as, for example, brominated compounds and polymers, metal containing compounds and phosphorus containing compounds, must be added to engineering plastics to impart fire resistance. However, such additives typically have deleterious effects on the processing characteristics, glass transition temperature, heat distortion temperature, optical clarity or other properties, and recently the use of halogenated and metal-containing flame retardant additives has been eliminated due to environmental concerns.
There is a need for fire resistant engineering polymer compositions that also possess an acceptable combination of properties including, for example, melt processability, mechanical properties, thermal stability, operating temperature, and the like, as well as a need to provide flame retardant engineering plastic formulations that do not include halogenated or metal containing flame retardant additives.
Embodiments of the invention are directed to a polymer composition including an engineering plastic; melamine or a derivative or salt thereof; and a linear or branched polyphosphonate or copolyphosphonate or combination thereof. In some embodiments, the engineering plastic may be about 15% to about 90% by weight of the total composition, and in certain embodiments, the engineering plastic may include without limitation polycarbonates polyacrylates, polyacrylonitriles, polyesters, polyamides, polystyrenes, polyureas, polyurethanes, polyepoxies, poly(acrylonitrile butadiene styrene)s, polyimides, polyarylates, poly(arylene ether)s, polyethylenes, polypropylenes, polyphenylene sulfides, poly(vinyl ester)s, polyvinyl chloride, bismaleimide polymer, polyanhydride, liquid crystalline polymer, cellulose polymer and copolymers and combinations thereof. In some embodiments, the engineering plastic may be poly(ethylene terephthalate), poly(butylene terephthalate), poly(naphthylene terephthalate) or mixtures or copolymers thereof, and in particular embodiments, the engineering plastic may be crystalline or semi-crystalline.
In some embodiments, the melamine or a derivative or salt thereof may be melamine cyanurate, and in other embodiments, the melamine or a derivative or salt thereof may be about 5% to about 20% by weight of the total composition.
In some embodiments, the linear or branched polyphosphonate of copolyphosphonate may have a weight average molecular weight (Mw) of at least about 20,000, and in certain embodiments, the linear or branched polyphosphonate or combination thereof is about 5% to about 40% by weight of the total composition. In particular embodiments, the linear or branched polyphosphonate or copolyphosphonate may include one or more blocks having one or more structural units of formula:
wherein n is an integer, and in some embodiments, the linear or branched polyphosphonate or copolyphosphonate further include one or more carbonates.
In still other embodiments, the polymer compositions of the invention may also include one or more components such as, for example, a filler, glass fibers, carbon fibers, inorganic fibers, organic fibers, fillers, surfactants, organic binders, polymeric binders, cross-linking agents, coupling agents, anti-dripping agents, TEFLON®, colorants, inks, dues, antioxidants and combinations thereof. In some embodiments, the composition may include TEFLON® up to about 1% by weight of the total composition, and in other embodiments, the composition may be up to about 40% by weight of the total composition glass fiber.
In certain embodiments, the linear or branched polyphosphonate or copolyphosphonate may be prepared from phosphonic diaryl ester that is distilled or wherein the linear or branched polyphosphonate or copolyphosphonate may be prepared from phosphonic acid diaryl ester that is undistilled.
Other embodiments of the invention include an article of manufacture produced from a polymer composition including an engineering plastic; melamine or a derivative or salt thereof; and a linear or branched polyphosphonate or copolyphosphonate or combination thereof. In some embodiments, the article may be fibers, films, coatings, moldings, foams, fiber reinforced articles or combinations thereof.
Yet other embodiments of the invention include a method for preparing a polymer composition including the steps of providing an engineering plastic and mixing into said engineering plastic a melamine, melamine salt or melamine derivative and a linear or branched polyphosphonate or copolyphosphonate or combination thereof. In some embodiments, the step of mixing may be performed in a melt. In other embodiments, the method may further include the steps of mixing glass fiber and TEFLON® into the engineering plastic, melamine, melamine salt or melamine derivative and a linear or branched polyphosphonate or copolyphosphonate or combination thereof. In particular embodiments, the step of mixing may include a first mixing step, wherein the engineering plastic and melamine, melamine salt or melamine derivative are combined; and a second mixing step, wherein the linear or branched polyphosphonate or copolyphosphonate and glass fiber are mixed into the combined engineering plastic and melamine, melamine salt or melamine derivative.
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Before the present compositions and methods are described, it is to be understood that this invention is not limited to the particular processes, compositions, or methodologies described, as these may vary. It is also to be understood that the terminology used in the description is for the purpose of describing the particular versions or embodiments only, and is not intended to limit the scope of the present invention which will be limited only by the appended claims.
It must be noted that, as used herein, and in the appended claims, the singular forms “a”, “an” and “the” include plural reference unless the context clearly dictates otherwise. Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art. Although any methods similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present invention, the preferred methods are now described. All publications and references mentioned herein are incorporated by reference. Nothing herein is to be construed as an admission that the invention is not entitled to antedate such disclosure by virtue of prior invention.
As used herein, the term “about” means plus or minus 10% of the numerical value of the number with which it is being used. Therefore, about 50% means in the range of 45%-55%.
“Optional” or “optionally” may be taken to mean that the subsequently described structure, event or circumstance may or may not occur, and that the description includes instances where the event occurs and instances where it does not.
The terms “flame retardant”, “flame resistant”, “fire resistant” or “fire resistance,” as used herein, mean that the composition exhibits a limiting oxygen index (LOI) of at least about 27 and/or a flame reference standard for electronic compositions UL-94.
The invention described herein is generally directed to flame retardant polymer compositions including at least one engineering polymer, at least one melamine, melamine salt or melamine derivative, and at least one linear or branched polyphosphonate or copolyphosphonate. Various embodiments of the flame retardant engineering polymer compositions of the invention may also include a reinforcement such as, for example, glass fibers which may provide the composites with a combination of fire resistance and dimensional stability while maintaining a high heat distortion temperature. Thus, the flame retardant compositions of the invention may exhibit a combination of properties that are near that of the unmodified engineering polymer.
The engineering plastics utilized in embodiments of the invention may be any engineering plastic known in the art. For example, in some embodiments, the engineering plastic may be a polymeric material such as, but not limited to, a polyester, polyamide, polycarbonate, polyacrylate, polyacrylonitrile, polystyrene, high impact strength polystyrene, syndiotactic polystyrene, poly(acrylonitrile butadiene styrene), polyurea, polyurethane, polyepoxy, polyimide, polyarylate, poly(arylene ether), polyethylene, polypropylene, polyphenylene sulfide, poly(vinyl ester), polyvinyl chloride, bismaleimide polymer, polyanhydride, and the like and copolymers of such materials. In other embodiments, the polymeric material used may be a liquid crystalline polymer, cellulose polymer, or any combination thereof, and in still other embodiments, the polymeric material may be a crystalline or semi-crystalline polymer. In particular embodiments, the engineering plastic may be a polyester, such as, but not limited to, poly(ethylene terephthalate), poly(naphthalene terephthalate), poly(butylene terephthalate) or mixtures or copolymers thereof.
Similarly, any linear or branched polyphosphonate or copolyphosphonate may be used in embodiments of the invention; however, in particular embodiments, linear or branched polyphosphonates and copolyphosphonates used may have a weight average molecular weight (Mw) of at least 20,000 g/mole as measured by gel permeation chromatography. In various embodiments, the linear or branched polyphosphonates or copolyphosphonates may be a known polyphosphonate or copolyphosphonate materials such as, for example, the polyphosphonates described in U.S. Pat. No. 6,861,499 entitled “Branched Polyphosphonates that Exhibit an Advantageous Combination of Properties, and Methods Related Thereto,” dated Mar. 1, 2005, which is hereby incorporated by reference in its entirety. Such polyphosphonates exhibit an exceptional combination of properties including fire resistance. In other embodiments, the linear or branched polyphosphonates and copolyphosphonates may be one or more linear or branched polyphosphonates described in, for example, U.S. Pat. Nos. 4,331,614, 2,716,101; 3,326,852; 4,328,174; 4,331,614; 4,374,971; 4,415,719; 5,216,113; 5,334,692; and 4,374,971, the disclosures of each of which are hereby incorporated by reference in their entireties.
Copolyphosphonates useful in certain embodiments of the invention are well known in the art. For example, in some embodiments, the copolyphosphonates used in the invention may be those described in U.S. Pat. Nos. 4,223,104; 4,322,520; 4,401,802; 4,481,350; 4,508,890; 4,762,905; 4,719,279; 4,782,123 or 4,332,921, the disclosures of each of which are hereby incorporated by reference in their entireties. In other embodiments of the invention, the copolyphosphonates used may be those described in U.S. Patent Publication No. 2007/0129511 entitled “Poly(Block-Phosphonato-Ester) And Poly(Block-Phosphonato-Carbonate) And Methods of Making Same,” filed on Jun. 7, 2007, the disclosure of which is hereby incorporated by reference in its entirety. The copolyphosphonates utilized in particular embodiments of the invention may contain at least about 50% phosphonate units, and in some embodiments, the copolyphosphonates used may be at least partially derived from monomers of diphenyl carbonate.
In certain embodiments, the linear or branched polyphosphonate or copolyphosphonate may include one or more structural units of general formula:
where n is an integer up to about 90. In some embodiments, such branched or linear polyphosphonates or copolyphosphonates may also include one or more carbonate structural units.
The linear or branched polyphosphonates or copolyphosphonates may be prepared by any method known in the art. However, the method by which the polyphosphonate or copolyphosphonate is prepared may effect the properties of the final mixture. For example, in some embodiments, the a polyphosphonate component may be prepared by polymerization of one or more diphenyl phosphonates (DPP) and one or more bisphenol, such as, bisphenol A (BPA). The DPP and bisphenol used may be prepared by any method and combined to form polyphosphonate by any method. Additionally, other components such as, for example, branching agents and catalysts may be used in such process. In some embodiments, the DPP may be distilled following its preparation to provide DPP that is substantially free of other components. In other embodiments, the DPP used in the preparation of the polysphosphonate may be undistilled. Without wishing to be bound by theory, polymer compositions such as those described in embodiments of the invention including polyphosphonates prepared from undistilled DPP may exhibit improved properties over those polymer compositions including polyphosphonates prepared from distilled DPP. For example, in some embodiments, polymer mixture including polyphosphonates prepared from undistilled DPP may exhibit improved melt flow viscosity and may improve the rate of reaction.
Melamine, melamine salts and melamine derivatives such as, for example, melamine cyanurate are well known in the art and any such compound may be utilized in various embodiments of the invention. Melamine and its salts and derivatives is used in a variety of applications and is commercially available, for example, melamine cyanurate is available from JLS Chemical Co.
The compositions of the invention may include any amount of any of the described components that allow for the composition to retain a good combination of properties while exhibiting flame resistance. For example, in some embodiments, the composition may contain from about 15% to about 90% by weight of the total composition of the engineering plastic. In other embodiments, the compositions of the invention may include about 5% to about 40% of the branched or linear polyphosphonate or copolyphosphonate by weight of the total composition, and in still other embodiments, the compositions of the invention may include about 5% to about 20% by weight of the total composition melamine, melamine salt or a melamine derivative.
The compositions of certain embodiments of the invention may also contain other components including, but not limited to, fillers, fibers, surfactants, binders, such as, organic binders or polymeric binders, crosslinking agents, coupling agents, anti-dripping agents, colorants, inks, dyes, antioxidants or any combination thereof. Fiber reinforced composites encompassed by the invention may include reinforcements that are continuous, woven, or chopped fibers including, but not limited to, glass fibers, carbon fibers, organic fibers or inorganic fibers such as silicon carbide and various combinations of such fibers. The use of the other components described above are well known and utilized in the art and any such other component combinations of other components may be used. For example, in particular embodiments, the compositions of the invention may include glass fibers and/or TEFLON®. Such additives may be included in the compositions of the invention at concentrations that are known and used in the art. For example, in embodiments in which glass fiber is included, the glass fiber may be up to about 40% by weight of the total composition, and in embodiments in which TEFLON® is provided, TEFLON® may be up to about 1% by weight of the total composition.
Without wishing to be bound by theory, the combination of melamine or its salts or derivatives with the linear or branched polyphosphonates or copolyphosphonates may provide the salient features of the compositions of the invention. Thus, these components may be combined with a variety of commodity engineering plastics to impart fire resistance without significantly detracting from the processing characteristics or thermal properties of the engineering plastics. The compositions of the invention may be self-extinguishing such that they stop burning when removed from a flame, and any drops produced by melting of these compositions in a flame may stop burning almost instantly and do not readily propagate fire to any surrounding materials. Moreover, the compositions of the invention may not evolve noticeable smoke when a flame is applied.
The engineering plastics encompassed by various embodiments of the invention may be useful in a wide variety of applications. For example, the engineering plastic compositions of the invention can be used as coatings, or they can be used to fabricate articles, such as free-standing films, fibers, foams, molded articles and fiber reinforced composites. Such articles may be well-suited for applications requiring fire resistance.
The components of the compositions of the invention may be combined by any method known in the art. For example, various embodiments of the invention include methods of manufacture of such compositions which include combining the components of the compositions in an internal mixing device such as, but not limited to, a banbury mixer, single screw extruder or twin screw extruder. Such mixers and extruders are well known and commonly used in the art. For example, twin screw extruders useful for the production of the flame resistant engineering plastics of embodiments of the invention are manufactured by, for example, Werner and Pdleiderer or Berstorff. In particular embodiments, the components of the composition (e.g., an engineering plastic, polyphosphonate or copolyphosphonate, melamine, melamine salt or melamine derivative, additives such as antioxidants, mold release compounds, anti-drip compounds and glass) may be melt blended by heating the components to a temperature of from about 200° C. to about 300° C. during extrusion, blending or mixing.
The sequence of addition of the components of the composition can vary throughout embodiments of the invention, and without wishing to be bound by theory, the specific properties (mechanical, rheological, flame retardancy) to be achieved may be effected by the order in which the components are added. For example, in some embodiments, all of the components of the composition may be combined simultaneously. In other embodiments, the engineering plastic may be melted and other components may be added while the melted engineering plastic is being mixed. In still other embodiments, glass fiber may be added at the end of the mixing process in, for example, a feeder located near the end of the extruder. The other components can be added either at the front, in the middle or at the end of the extruder and any combination thereof. Without wishing to be bound by theory, adding glass fiber at the end of the mixing process may minimize the reduction of the aspect ratio of glass fibers in the composition.
In particular embodiments, the engineering plastic may be mixed with the melamine, melamine salt or melamine derivative in a first step, and the glass and branched or linear polyphosphonate or copolyphosphonate may be added in a second step near the end of the mixing process. For example, the engineering plastic and the melamine, melamine salt or melamine derivative may be combined and mixed and the polyphosphonate or copolyphosphonate and glass may be added near the end of the mixing process or at a feeder located near the end of an extruder. In such embodiments, the polymer composition prepared may exhibit improved properties over polymer compositions prepared by either combining all of the components simultaneously or mixing the linear or branched polyphosphonate or copolyphosphonate to the engineering plastic and melamine, melamine salt or melamine derivative simultaneously. For example, polymer compositions in which the linear or branched polyphosphonate or copolyphosphonate is added at the end of the mixing process may exhibit improved heat distortion temperature (HDT), improved impact strength and improved elongation over similar polymer compositions prepared by mixing in the linear or branched polyphosphonate or copolyphosphonate at the beginning of the mixing process.
The engineering plastic compositions described herein and prepared using such methods generally exhibit a combination of properties that include improved fire resistance when compared to engineering polymer compositions that contain monomeric or oligomeric phosphorus or melamine containing flame retardants. The engineering plastic compositions of the invention also exhibit fire resistance that is at least equal to and, in some embodiments, is superior to that of engineering plastics compositions that contain halogenated or metal containing flame retardants. Additionally, the engineering plastics compositions of embodiments of the invention also provide excellent high temperature performance, high modulus, good toughness and improved low viscosity compared to the engineering plastics alone.
Having generally described the invention, a more complete understanding thereof may be obtained by reference to the following examples that are provided for purposes of illustration only and do not limit the invention.
Into 12 L reactor equipped with a distillation column and mechanical stirrer was placed 3.329 kg of 2,2-bis-(4-hydroxyphenyl) propane (bisphenol A), 600 mg sodium phenolate catalyst, 89 g 1,1,1 tris(4-hydroxy phenyl)ethane and 3726 g methylphosphonic acid diphenyl ester (diphenylmethylphosphonate). The mixture was heated from 250° C. to 300° C. with reduced pressure from 150 mm Hg to 1.5 mm Hg over about 15 hours period. An additional 600 mg of sodium phenolate catalyst was added at 11 hours. A noticeable, rapid increase in melt viscosity was observed over the last hour of the reaction.
Approximately 3372 g of distillate was collected over the course of the reaction. The polyphosphonate was extruded out of the reactor into a water bath to form a strand and subsequently pelletized to yield 3827 g of polyphosphonate. The branched polyphosphonate was 10.8% phosphorous, transparent, colorless and tough and exhibited a Tg of 103° C. The product was not fully soluble in methylene chloride after 12 hours.
Poly(butylene terephthalate) (PBT, PF300G6 from Polyram, Inc) including 30% by weight glass fiber was melt mixed 0.6% by weight poly(tetrafluoroethylene) (TEFLON® 6C-N) with no polyphosphonate (Example 1) or 0.6% by weight TEFLON® with 30% by weight of the branched polyphosphonate prepared as described above (FRX) (Example 2). These compositions were fabricated into test articles by injection molding. These fabricated articles were then tested for toughness using the notched Izod impact method; heat distortion temperature (HDT) under 1.82 MPa; and fire resistance using the UL 94 method on 0.8 mm thick specimens.
PBT containing 30% by weight glass fiber was melt mixed with 0.6% by weight poly(tetrafluoroethylene) and no polyphosphonate (Example 1) or 0.6% by weight TEFLON® and 15% by weight melamine cyanurate (MC, JLS-MC810D from JLS Chemical Co.) (Example 3) or 0.6% by weight TEFLON® and 30% by weight MC (Example 4). The compositions were then fabricated into test articles by injection molding. These fabricated articles were then tested for toughness using the notched Izod impact method; HDT under 1.82 MPa; and fire resistance using the UL 94 method on 0.8 mm thick specimens.
PBT containing 30% by weight glass fiber was melt mixed with 0.6% by weight TEFLON®, 15% by weight MC and 15% by weight FRX (Example 5) or 0.6% by weight TEFLON®, 20% be weight MC and 10% by weight FRX (Example 6). In both Example 5 and Example 6, PBT made up 48.6% by weight of the total composition. The compositions were fabricated into test articles by injection molding. These fabricated articles were then tested for toughness using the notched Izod impact method; HDT under 1.82 MPa; and fire resistance using the UL 94 method on 0.8 mm thick specimens.
The composition examples 1-6 in percent by weight for the total composition are presented in Table 1, and the results of thermal mechanical and fire testing are presented in Table 2.
As indicated in Table 2, glass filled PBT has good notched impact strength and HDT, but is not fire resistant (Example 1). Glass filled PBT compounded with TEFLON® and polyphosphonate (FRX) (Example 2), exhibit excellent fire resistance but the compositions demonstrate a dramatic reduction in heat distortion temperature and poor notched impact strength. Glass filled PBT compounded with TEFLON® and MC (Examples 3 and 4) exhibit good HDT and notched impact strength but is not fire resistant. As illustrated in Examples 5 and 6, glass filled PBT compounded with TEFLON®, MC and FRX exhibits an excellent combination of HDT, notched impact strength and fire resistance.
In a reaction flask equipped with an overhead stirrer, N2 inlet, a thermometer and a condenser, triphenylphosphite (TPP) and iodomethane were mixed together at room temperature and then heated under N2 to 240° C. No exotherm observed at this point. Dark purple discoloration is noted during heating. The addition of trimethylphosphite (TMP(i)) from the feeding funnel begins when the reaction temperature reaches 240° C. and proceeds from 3.0 to 3.5 hours. No refluxing is observed during TMP(i) feeding, but noted dark purple discoloration disappears soon after the addition of TMP(i) begins. Following the addition of TMP(i), the reaction temperature is maintained at 240° C. to 260° C. for 3.5 hours. The reaction is terminated after a gas chromatography (GC) indicates that no trace of the starting materials is detected. The crude product may then be distilled to remove other components.
Both undistilled DPP (example 7a) and distilled DPP (example 7b) were used to prepare polyphosphonates as follows:
Into 6 L reactor equipped with a distillation column and mechanical stirrer was placed the 1.308 kg (5.737 mol) of 2,2-bis-(4-hydroxyphenyl) propane (bisphenol A) distilled 1467 g (5.915 mol) of diphenyl methylphosphonate (Example 9b), 35.1 g 1,1,1 tris(4-hyroxphenyl)ethane, 120 mg sodium phenolate (NaOPh) catalyst, 225 mg tetraphenylphosphonium phenolate (TPPOP) which is a chemical complex of tetraphenylphosphonium phenolate and phenol consisting of about 70% and about 30% of each, respectively (m.p. 145° C.). The mixture was heated from 250° C. to 300° C. while reducing the pressure from 150 to 1.5 mm Hg over about 10 hours. A noticeable, rapid increase in solution viscosity of the melt was observed over the last hour of the reaction. Approximately 1227 g of distillate was collected over the course of the reaction. The polyphosphonate was extruded out of the reactor into a water bath to form a strand that was subsequently pelletized and resulted in a yield of 1476 g of polyphosphonate.
The polyphosphonate prepared from undistilled DPP (example 8a) was transparent, nearly colorless and tough with a Tg of 104° C. and a 10.8% phosphorous. The product was not fully soluble as 0.5% solution in Methylene chloride after 12 hours
The polyphosphonate prepared from distilled DPP (example 8b) was transparent, nearly colorless and tough and exhibited a rel=1.41 (measured as 0.5% solution in CH2Cl2) and a Tg of 106° C. The percentage of phosphorous in this polymer was 10.8%. The molecular weight, measured by GPC with refractive index detector based on PS standard, showed Mn=10657 and an Mw=75955 with a polydispersity of 7.1.
In this example, the polyphosphonate produced from a undistilled diphenyl methylphosphonate (Example 8a) was used.
Into a twin screw extruder are added 10% by weight MC, 39.5% by weight PBT, 20% by weight polyphosphonate prepared as described in Example 8a, 30% by weight glass fiber and 0.5% by weight TEFLON®. All ingredients other then glass were added at the front of the extruder and glass at the end of the extruder. The extruder is operated at a temperature range of between 230° C. to 280° C. and at a screw RPM of 100 to 5000.
Resulting Properties:
Tensile Strength at break: 121 Mpa
Elongation at break: 1.3%
MFR (250 C/5 Kg): 51 g/10 min
In this example, we use a polyphosphonate produced from a diphenyl methyl phosphonate manufactured via the method described in Example 8b.
Into a twin screw extruder are added 10% by weight MC, 39.5% by weight PBT, 20% by weight branched polyphosphonate prepared as described in example 8b, 30% by weight glass fiber and 0.5% by weight TEFLON®. All ingredients other then glass were added at the front of the extruder and glass at the end of the extruder. Alternatively, the polyphosphonate can be added together with the glass at the end of the extruder and all other ingredients at the front of the extruder. The extruder is operated at a temperature range of between 230° C. to 280° C. and at a screw RPM of 100 to 5000.
Resulting Properties:
Tensile Strength at break: 118 Mpa
Elongation at break: 1.4%
MFR (250 C/5 Kg): 17 g/10 min
Polyphosphonate prepared from distilled DPP (example 8b) was used in the following example.
Into a twin screw extruder were added 39% by weight PBT, 15% by weight MC, 15% by weight polyphosphonate prepared from distilled DPP as described in Example 8b, 0.6% by weight TEFLON and 0.4% by weight additives, and these components were mixed. Through a feeder at the end of the extruder, 30% by weight glass fiber was added to produce polymer mixture example 11a, or
Into a twin screw extruder were added 39% by weight PBT, 10% by weight MC, 0.6% by weight TEFLON and 0.4% by weight additives, and these components were mixed. Through a feeder at the end of the extruder, 15% by weight polyphosphonate prepared from distilled DPP as described in Example 8b and 30% by weight glass fiber were added to produce polymer mixture example 11b.
This application is a continuation of U.S. application Ser. No. 12/173,992 entitled “Flame Retardant Engineering Polymer Compositions,” filed Jul. 16, 2008, which claims the benefit of priority from U.S. Provisional Application No. 60/949,970 entitled “Flame Retardant Engineering Polymer Compositions,” filed Jul. 16, 2007, the contents of which are hereby incorporated by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| 60949970 | Jul 2007 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12173992 | Jul 2008 | US |
| Child | 14682537 | US |
