Flame-resistant flexible polyurethane foams

Abstract

Polyurethane foam compositions may contain a polymer matrix prepared by curing a reaction mixture containing an isocyanate-reactive component including one or more polyether polyols having a hydroxyl number from 25 to 100 mg KOH / g, as determined in accordance with ASTM D4274, and having from two to eight hydroxyl groups per molecule; one or more hydroxyl-terminated prepolymers; an FR additive component comprising an ammonium polyphosphate and an alkaline earth metal carbonate in a weight ratio of from 1.3:1 to 6.5:1, and present at a percent by weight of the isocyanate-reactive component (wt%) ranging from 6 wt% to 50 wt%; and an isocyanate component including one or more polyisocyanates.

Description

[0001] FLAME-RESISTANT FLEXIBLE POLYURETHANE FOAMS FIELD Embodiments relate to self-extinguishing, high density, semi-rigid / flex polyurethane foam compositions containing a mixture of solid flame resistance additives. BACKGROUND Polyurethane (PU) foams, including flexible PU foams, find use in a variety of applications across the automotive industry, including high temperature environments such as engine compartments. While flexible PU foams are desirable for workability during installation, flexible PU foams are flammable and tend to melt and drip when exposed to heat and flame. Further, the flexible polyurethane foams may smolder after the flames have been extinguished. Safety hazards have prompted regulation for self-extinguishing materials, particularly for engine encapsulation, leading to the development of standards such as Volkswagen’s TL 52722 standard (e.g, as determined by PV3357 testing), and the Underwriters' Laboratories Standard 94 (UL 94) V-0 rating system. These tests determine burning behavior resulting from surface and edge flame exposure, measuring the response of the foam to the fire after the ignition source is removed. For most standards, the flexible polyurethane foam must not continue to burn once the flame is removed (be self-extinguishing); and any dripping flexible polyurethane foam must not continue to burn. While various flame resistance (FR) additives are included in PU foam formulations to improve FR properties to meet industry and regulatory requirements, popular solutions such as melamine and halogen-based compounds can affect the color and quality of PU foams over time. Further, chemical FR additives may be volatile and the FR performance of the materials can change over time, and present hazards in terms of environmental and health safety. Summary In an aspect, embodiments disclosed herein are directed to polyurethane foam compositions containing a polymer matrix prepared by curing a reaction mixture containing an isocyanate-reactive component including one or more polyether polyols having a hydroxyl number from 25 to 100 mg KOH / g, as determined in accordance with ASTM D4274, and having from two to eight hydroxyl groups per molecule; one or more hydroxyl-terminated prepolymers; an FR additive component comprising an ammonium polyphosphate and an alkaline earth metal carbonate in a weight ratio of from 1.3:1 to 6.5:1, and present at a percent by weight of the isocyanate-reactive component (wt%) ranging from 6 wt% to 50 wt%; and an isocyanate component including one or more polyisocyanates. Polyurethane foams and foam-forming compositions may include an FR additive component containing a mixture of ammonium polyphosphate, metal carbonate, and expandable graphite in some embodiments. In another aspect, embodiments disclosed herein are directed to a two-component polyurethane composition containing: an isocyanate-reactive component containing: one or more polyether polyols having a hydroxyl number from 25 to 100 mg KOH / g, as determined in accordance with ASTM D4274, and having from two to eight hydroxyl groups per molecule; one or more hydroxyl-terminated prepolymers; an additive component including ammonium polyphosphate and alkaline earth metal carbonate in a weight ratio of from 1.3:1 to 6.5:1, the additive component being present in amount from 6 part by weight to 50 parts by weight, based on 100 parts by weight of the polyol component; and an isocyanate component including one or more polyisocyanates. Two-component polyurethane compositions may include an FR additive component containing a mixture of ammonium polyphosphate, metal carbonate, and expandable graphite in some embodiments. Detailed Description Embodiments relate to self-extinguishing, flexible polyurethane (PU) foam compositions containing a mixture flame resistance (FR) additives, which may include one or more of ammonium polyphosphate, metal carbonate, and expanded graphite. PU foam compositions may a final foam density of 200 kg / m3or more and pass PV3357 testing and / or achieve a UL-94 vertical rating of V1 or better. Further, PU foam compositions exhibit improved performance without the use of either melamine and / or halogen-containing FR additives. PU foam compositions disclosed herein generally include the product obtained from combining a two-component curable composition: an isocyanate-reactive component (“A-side”) and an isocyanate component (“B-side”). During application, the isocyanate (B) and isocyanate- reactive components (A) are mixed, initiating a curing reaction, and forming a polyurethane foam and / or article. PU foam compositions may also include one or more fillers added to the isocyanate (B) and / or isocyanate-reactive components (A), or as a third component (C) added during mixing. A.) Isocyanate-reactive component The isocyanate-reactive component (or A-side) may contain of one or more of polyether polyols, hydroxy-terminated prepolymers, chain extenders, polyester polyols, fillers, and other additives. PU compositions may include an isocyanate-reactive component at a percent by weight (wt%) ranging from 20 wt% to 85 wt%, 20 wt% to 80 wt%, or 25 wt% to 80 wt%. In some embodiments, the isocyanate-reactive component includes one or more polyether polyols. Polyether polyols are prepared by polyaddition of alkylene oxides such as propylene oxide and / or ethylene oxide onto polyhydroxy functional starter compounds in the presence of catalysts known in the art. Polyether polyols may be prepared from a starter compound and one or more alkylene oxides, for example, ethylene oxide, propylene oxide, and / or butylene oxide. Starter compounds may include, but are not limited to, molecules having 1 to 8 hydroxyl groups per molecule, such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, l,4-butanediol, l,6-hexanediol, triethanolamine, diethanolamine, diisopropanolamine, bisphenol A, glycerol, diglycerol, triglycerol, trimethylolpropane, di(trimethylolpropane) pentaerythritol, dipentaerythritol, tripentaerythritol, sugars and sugar alcohols such as sucrose and sorbitol, and the like. Polyether polyols may be a blend of any of these polyether polyols together with one or more starter compounds, and the polyether polyols can also be one or more starter compounds themselves. Polyether polyols may also include polyols reacted with polyethers formed from copolymers of alkylene oxides, including block copolymers and polyethers “capped” with hydroxyethyl and / or hydroxypropyl oligomers or polymers. In some cases, the one or more polyether polyols contained in the isocyanate-reactive component may have an average hydroxyl group number of no less than 80 mg KOH / g, such as in a range from 80 to 800 mg KOH / g, or from 200 to 400 mg KOH / g. Polyols in the isocyanate-reactive component may have a hydroxyl equivalent weight (HEW) ranging from 100 to 4000. In some cases, isocyanate-reactive component may include a mixture low (“Type A”) and high (“Type B”) hydroxy number (OH#) polyether polyols. Type A polyether polyols may have an OH# according to ASTM D4274 ranging from 20 mg KOH / g to 50 mg KOH / g, and a functionality ranging from 1.5 to 6. Type A polyether polyols may be capped with oligomers or polymers of ethylene oxide (EO-capped) that modify elongation properties and toughness when compared to rigid foams of similar density. EO-capped Type A polyether polyols may have an ethylene oxide (EO) content at a percent by weight (wt%) of 3 wt% to 80 wt%, 3 wt% to 50 wt%, or 3 wt% to 30 wt%. Type B polyether polyols may have an OH# according to ASTM D4274 ranging from 200 KOH / g to 600 KOH / g, and a functionality of 2 to 6. Isocyanate-reactive components may include a Type A polyether polyol at a percent by weight (wt%) of the sum of all polyols in an isocyanate-reactive component ranging from 10 wt% to 90 wt%, or 20 wt% to 90 wt%. The weight ratio of Type A:Type B polyether polyols may be in the range of 5:1 to 1:5, 5:1 to 1:1, 4:1 to 1:4, 3:1 to 1:3, or 3:1 to 1:1. In some cases, PU foam compositions may include an isocyanate-reactive component containing one or more “multi-functional” polyether polyols having a functionality of 3 or more. For example, multi-functional polyether polyols may be generated by the polyaddition of alkylene oxide in the presence of a starter compound having a functionality of 3 or more. Multi-functional polyether polyols may have a hydroxy functionality ranging from 3 to 8, or 3 to 7. Polyether polyols may have a hydroxyl number (OH#) according to ASTM D4274-21 in a range of 200 mg KOH / g to 700 mg KOH / g, or 200 mg KOH / g to 600 mg KOH / g. Isocyanate-reactive components disclosed herein may include a total polyether polyol content at a percent by weight (wt%) ranging from 10 wt% to 50 wt%, 10 wt% to 45 wt%, or 10 wt% to 30 wt%. Isocyanate-reactive components disclosed herein may include one or more hydroxy- terminated isocyanate prepolymers, also known as copolymer polyols (CPP). Hydroxy-terminated prepolymers may be any prepolymer(s) prepared by the reaction of one or more polyisocyanates containing two or more isocyanate groups with a stoichiometric excess of polyols (e.g., polyether polyols, starter compounds described above, etc.). By using the polyol materials in excess, the isocyanate prepolymer can be provided with hydroxyl functionality. In general, hydroxyl- terminated prepolymers can be prepared using the same starting materials as described above, the difference being in the relative ratios of components. Hydroxyl-terminated isocyanate prepolymers may have a density according to ASTM D3574-17 Test A of less than 2 g / mL, or in a range of 0.5 g / mL to 1.9 g / mL, or 0.7 g / mL to 1.9. Isocyanate-reactive components disclosed herein may include one or more hydroxyl- terminated isocyanate prepolymers at a percent by weight (wt%) ranging from 10 wt% to 50 wt%, 10 wt% to 45 wt%, or 10 wt% to 30 wt%. Isocyanate-reactive components disclosed herein may include one or more polyester polyols produced by the reaction of one or more carboxylic diacids and polyols having an OH functionality 2 to 4. Suitable carboxylic acids may include aromatic diacids or anhydrides such as phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, methyl esters of phthalic, isophthalic, or terephthalic acid, dimethyl terephthalate, trimellitic anhydride, pyromellitic dianhydride, or mixtures thereof; and C4 to C12 aliphatic diacids. Suitable polyols for the formation of polyesters include one or more alkylene glycols or polyalkylene glycols having a hydroxy functionality of 2 to 4, such as ethylene glycol, 1,2- or 1,3-propylene glycol, 1,4- butanediol, 1,6-hexanediol, diethylene glycol, glycerine, and the like. Example polyester polyols include polyesters of phthalic anhydride and diethylene glycol, and polyesters of a C4 to C12 diacid such as succinic acid or adipic acid and diethylene glycol. Polyester polyols may have an average hydroxyl number (OH number) as determined according to ASTM D4274-21 in a range of 100 mg KOH / g to 500 mg KOH / g, 150 mg KOH / g to 450 mg KOH / g, or 150 mg KOH / g to 450 mg KOH / g. Isocyanate-reactive components may include one or more polyester polyols at a percent by weight (wt%) ranging from 10 wt% to 40 wt%, from 15 wt% to 35 wt%, or from 15 wt% to 30 wt%. Isocyanate-reactive components disclosed herein may include one or more chain extenders to modify the overall molecular weight of the polyurethane and improve mechanical properties. Suitable chain extenders may have a functionality of at least two, and may include 1,3- propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexandiol, 1,7-heptanediol, 1,2-dodecanediol, cyclohexanedimethanol, 3-methyl-l,5-pentanediol, 2,4-diethyl-1,5-pentanediol, bis(2- hydroxyethyl)ether, bis(6-hydroxyhexyl)ether, and the like. Isocyanate-reactive components may include one or more chain extenders at a percent by weight (wt%) ranging from 0.5 wt% to 15 wt%, 1 wt% to 15 wt%, or 3 wt% to 7 wt%. Isocyanate-reactive components may include one or more flame resistance (FR) additives, which may include a mixture of an ammonium polyphosphate (APP) and an alkaline earth metal carbonate. FR additives may include APP and, in some cases, the APP may have a total nitrogen content as a percent by weight (wt%) from about 5 wt% to about 15 wt%, and a total phosphorus content from about 30 wt% to about 40 wt%, based on the total weight of the APP. Isocyanate- reactive components may include APP at a percent by weight (wt%) ranging from 0.5 wt% to 15 wt%, 1 wt% to 12.5 wt%, or 1 wt% to 10 wt%. FR additives may include one or more metal carbonates (MC) such as calcium carbonate, magnesium carbonate, and the like. Isocyanate-reactive components may include one or more MC at a percent by weight (wt%) ranging from 0.5 wt% to 4 wt%, 0.5 wt% to 3 wt%, or 0.5 wt% to 2.5 wt%. Isocyanate-reactive components may include a combination of APP and MC in a weight ratio of APP:MC ranging from 1.3:1 to 6.5:1, 1:2 to 5:1, 1:1 to 5:1; or 1:2 to 4:1. FR additives may include an expandable graphite (EG) (alternatively exfoliated graphite). EG may be present as particles having a d50 particle size from 200 µm to 300 µm. Isocyanate- reactive components may include one or more EG at a percent by weight (wt%) ranging from 4 wt% to 15 wt%, 5 wt% to 12.5 wt%, or 5.5 wt% to 10 wt%. Isocyanate-reactive component may include an FR additive containing a mixture of APP, MC and EG at a weight ratio of (APP+CC):EG ranging from 0.1:1 to 0.7:1, 1.3:1 to 6.5:1, or 1:1 to 5:1, and present at a percent by weight of the isocyanate-reactive component (wt%) ranging from 6 wt% to 14 wt%, or 6 wt% to 50 wt%. In some cases, isocyanate-reactive component may include an FR additive containing a mixture of APP, MC and EG at a weight ratio of (APP+CC):EG ranging from 0.1:1 to 3:1 and present at a percent by weight of the isocyanate-reactive component (wt%) ranging from 6 wt% to 50 wt%, or 15 wt% to 50 wt%, where the weight ratio of APP:CC may range from 0.1:1 to 0.7:1, 1.3:1 to 6.5:1, or 1:1 to 5:1, and the ratio (APP+CC):EG is the ratio of the total weight of APP and CC to EG. Isocyanate-reactive components disclosed herein may include a total concentration of FR additives (defined as APP, CC, and EG) at a percent by weight (wt%) of 5 wt% or more to 50 wt% or less, such as in a range of 5 wt% to 50 wt%, 6 wt% to 40 wt%, or 10 wt% to 40 wt%. PU foam compositions may include one or more fillers including fiberglass, fiber, carbon fiber silica, CaCO3, kaolin, talc, alumina, alumina trihydrate (ATH), and the like. One or more fillers may be added at a percent by weight (wt%) of the composition ranging from 0 wt% to 25 wt%, or 1 wt% to 20 wt%. In some cases, fillers may be added to the isocyanate component and / or the isocyanate-reactive component in amount sufficient to provide the mixture with the corresponding weight percentages above. Isocyanate-reactive components may include one or more catalysts for enhancing polyurethane polymerization to generate the PU foam composition. Catalysts may be used individually or as a catalyst package containing multiple catalysts, such as gelling catalysts, blowing catalysts, and trimerization catalysts. Gelling and blowing catalysts may be differentiated by a tendency to favor either the urethane (gel) reaction, in the case of the gelling catalyst, or the urea (blow) reaction, in the case of the blowing catalyst. A trimerization catalyst may be utilized to promote the isocyanurate forming reaction in the compositions. The catalyst package can also be added as a separate stream into the reaction mixture of isocyanate and isocyanate-reactive components. Gelling catalysts include organometallic compounds, cyclic tertiary amines and / or long chain amines, e.g., that contain several nitrogen atoms and combinations thereof. Organometallic compounds include organotin compounds, such as tin(II) salts of organic carboxylic acids, e.g., tin(II) diacetate, tin(II) dioctanoate, tin(II) diethylhexanoate, and tin(II) dilaurate, and dialkyltin(IV) salts of organic carboxylic acids, e.g., dibutyltin diacetate, dibutyltin dilaurate, dibutyltin maleate and dioctyltin diacetate. Bismuth salts of organic carboxylic acids may also be utilized as the gelling catalyst, such as, for example, bismuth octanoate. Cyclic tertiary amines and / or long chain amines include dimethylbenzylamine, triethylenediamine, and combinations thereof. Examples of a commercially available gelling catalysts are POLYCAT®8, DABCO®33-LV, and DABCO®T-12 from Evonik, among other commercially available gelling catalysts. Blowing catalysts may include bis-(2-dimethylaminoethyl) ether, pentamethyldiethylenetriamine, triethylamine, tributyl amine, N,N-dimethylaminopropylamine, diethanolamine, dimethylethanolamine, N,N,N′,N′-tetra-methylethylenediamine, and combinations thereof, among others. An example of a commercial blowing catalyst is POLYCAT®5, from Evonik, among other commercially available blowing catalysts. Trimerization catalysts may include any such catalysts known in the art. Examples of trimerization catalysts include N,N',N''-tris(3-dimethylaminopropyl) hexahydro-S-triazine; N,N- dimethylcyclo-hexylamine; 1,3,5-tris(N,N-dimethylaminopropyl)-s-hexahydrotriazine; [2,4,6-tris (dimethylaminomethyl) phenol]; potassium acetate, potassium octoate; tetraalkylammonium hydroxides such as tetramethylammonium hydroxide; alkali metal hydroxides such as sodium hydroxide; alkali metal alkoxides such as sodium methoxide and potassium isopropoxide; and alkali metal salts of long-chain fatty acids having 10 carbon atoms to 20 carbon atoms, and combinations thereof, among others. Some commercially available trimerization catalysts include, for example, DABCO®TMR-2, DABCO®TMR-20, DABCO®TMR-30, DABCO®TMR-7, DABCO®K 2097; DABCO®K15, POLYCAT®41, and POLYCAT®46, each from Evonik, among other commercially available trimerization catalysts. Catalysts may include a “latent catalyst” or “delayed catalyst,” which is defined as a catalyst compound that is of low catalytic activity or is relatively inactive at ambient temperatures, and which becomes more catalytically active, such as by disassociation, decoordination, ring opening, ionization, or tautomerization upon heating to effect catalysis of least one of the chemical reactions involved in making a PU foam. Ambient temperatures may range from 18 °C to 35 °C. Latent / delayed catalysts can be gelling, blowing, and / or trimerization types of catalysts in terms of their function in the foaming process. The latent catalyst is often a subset of tertiary amine gelling catalysts (e.g., delayed action tertiary amine based on 1,8- Diazabicyclo[5.4.0]undec-7-ene) that include acid salts, phenolic salts, or complexes of a tertiary amine catalyst where the acid or phenolic is often a carboxylic acid or phenol species, but not limited to, such as formic acid, acetic acid, propionic acid, 2-ethylhexanoic acid, phenoxyacetic acid, gluconic acid, tataric acid, citric acid, phenol, nonylphenol, diisopropyl phenol, and the like; and mixtures thereof. Some useable commercially available latent catalysts include, for example, DABCO®TMR-30, POLYCAT®SA2 LE, POLYCAT®SA-1 / 10, and DABCO®8154 from Evonik; NIAX®A-107, NIAX®C-31, and NIAX®C-225 from Momentive; and JEFFCAT®ZF- 54, JEFFCAT®LED-204 from Huntsman Corporation; and mixtures thereof. The catalyst or catalyst package may be present in the PU foam composition at a percent by weight (wt%) ranging from 0.1 wt% to 10 wt%, or 0.1 wt% to 3 wt%. In some cases, a catalyst package may be added to the isocyanate-reactive component in amount sufficient to provide the mixture with the corresponding weight percentages above. B.) Isocyanate component The isocyanate component (or B-side) may contain one or more isocyanate compounds, such as polymeric isocyanates, aromatic isocyanates, or carbodiimide-modified isocyanates. Isocyanate compounds may be monomeric, oligomeric, prepolymers, and the like. The isocyanate component can include, for example, one or more isocyanate and / or polyisocyanate compounds. Isocyanate components may include isocyanate compounds having a nominal functionality of greater than 1.5, greater than 2.0, or in a range of 1.5 to 4. Polyurethane compositions and foam- forming mixtures may include an isocyanate component at a percent by weight (wt%) ranging from 15 wt% to 80 wt%, 20 wt% to 80 wt%, or 25 wt% to 70 wt%. The isocyanate component may include an isocyanate compound having a number average molecular weight of 150 g / mol to 750 g / mol. In some cases, the isocyanate compound can have a number average molecular weight from a low value of 150 g / mol, 200 g / mol, 250 g / mol or 300 g / mol to an upper value of 350 g / mol, 400 g / mol, 450 g / mol, 500 g / mol or 750 g / mol. The number average molecular weight values reported herein are determined by end group analysis, gel permeation chromatography, and other methods as is known in the art. The isocyanate compound can be monomeric and / or polymeric, as are known in the art. In some cases, isocyanate components may include isocyanate compounds having an isocyanate content by weight of 10% or more, 20% or more, or 30% or more, or in a range of 10% to 50%. The isocyanate component may include on or more of aliphatic polyisocyanate, cycloaliphatic polyisocyanate, araliphatic polyisocyanate, aromatic polyisocyanate, and the like. Examples of isocyanates include, but are not limited to, polymethylene polyphenylisocyanate; toluene 2,4- / 2,6-diisocyanate (TDI); methylenediphenyl diisocyanate (MDI, including its isomers); polymeric and prepolymeric MDI; triisocyanatononane (TIN); naphthyl diisocyanate (NDI); 4,4’-diisocyanatodicyclohexyl-methane; 3-isocyanatomethyl-3,3,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate, IPDI); tetramethylene diisocyanate; hexamethylene diisocyanate (HDI); 2-methyl-pentamethylene diisocyanate; 2,2,4-trimethylhexamethylene diisocyanate (THDI); dodecamethylene diisocyanate; 1,4-diisocyanatocyclohexane; 4,4’- diisocyanato-3,3’-dimethyl-dicyclohexylmethane; 4,4’-diisocyanato-2,2-dicyclohexylpropane; 3- isocyanatomethyl-1-methyl-1-isocyanatocyclohexane (MCI); 1,3 -diisooctylcyanato-4 - methylcyclohexane; 1,3 -diisocyanato-2-methylcyclohexane; and combinations thereof, among others. In addition to the isocyanates mentioned above, modified or partially modified polyisocyanates including uretdione, isocyanurate, carbodiimide, uretonimine, allophanate or biuret structures, and combinations thereof, among others, may be utilized. For example, isocyanate compounds may include carbodiimide modified MDI. Isocyanate compounds may include isocyanate prepolymers resulting from reaction of an isocyanate-reactive compound with a molar excess of an isocyanate compound or polymeric isocyanate compound under conditions that do not lead to gelation or solidification, the isocyanate prepolymers can have a higher average isocyanate equivalent weight of > 400 g / eq. Formation of isocyanate prepolymers is known in the art, and may include reacting (1) at least one isocyanate compound and (2) at least one polyol compound. Isocyanate prepolymers may be described by an isocyanate index, defined as the ratio of isocyanate groups to isocyanate-reactive groups (such as OH groups) multiplied by 100. Isocyanate prepolymers disclosed herein may have an isocyanate index, defined as the equivalents of isocyanate divided by the total equivalents of isocyanate- reactive hydrogen containing materials, multiplied by 100) in a range of from 30 to 400, 40 to 300, or 40 to 200. Examples of commercial isocyanates include, but are not limited to, polyisocyanates under the trade names VORANATE™, PAPI™ , VORATRON™, VORAFORCE™, and ISONATE™, all of which are available from The Dow Chemical Company. Isocyanate-reactive components may include a polyol blend containing one or more polyether polyols, polyester polyols, aliphatic polyols, polyol crosslinkers, and hollow particles, and other additives such as catalysts, surfactants, and the like. In the foam forming compositions, and the methods for making it, suitable amounts of the isocyanate component may range from the amount needed to provide a foam forming composition having an isocyanate index of from 75 to 105 (e.g., from 70 to 100 , etc.). As used herein, unless otherwise indicated, the term “isocyanate index” or simply “index” refers to the ratio of the number of equivalents of isocyanate functional groups to the number of equivalents of active hydrogen, e.g. hydroxyl groups, in a given polyurethane forming reaction mixture, multiplied by 100 and expressed as a number. For example, in a reaction mixture wherein the number of equivalents of isocyanate equals the number of equivalents of active hydrogen, the isocyanate index is 100. As used herein, the term “isocyanate reactive group” refers to an active hydrogen, such as a hydrogen in a hydroxyl group. C. Method of Preparation For PU foam compositions disclosed herein may be achieved by mixing the respective components of the isocyanate component and the isocyanate-reactive component in any sequence and allowing the mixture to cure. Suitable mixing techniques include the use of a Ross PD Mixer (Charles Ross), Myers mixer, FlackTek Speedmixer, butterfly mixer and the like. Various components of the composition could also be mixed using a continuous process. Methods for making PU foams may include, e.g., forming the isocyanate-reactive component comprising the one or more or a mixture of polyether polyols and the additive combination of ammonium polyphosphate flame retardant and calcium carbonate; and, combining the polyol component with the isocyanate component. The combining may further comprise combining the isocyanate reactive component with isocyanate component to form a reactive mixture. The reactive mixture may then be poured into a mold, such as an open mold or a closed mold. Molding using a closed molding or molding under pressure facilitates formation of higher resilience foams and / or may be free rise. An alternative method may comprise the reaction of the various components such as isocyanate, polyol, catalyst, and additives, that are processed according to continuous slabstock foam production process, typically used for the production on conventional flex foam. Polyurethane foam-forming compositions may form foams and foam articles having a density according to ISO 845 in a range of 150 kg / m3to 500 kg / m3, 150 kg / m3to 300 kg / m3, or 200 kg / m3to 250 kg / m3. Polyurethane foam-forming compositions may form foams and foam articles having an elongation at break according to DIN EN ISO 1798 of 60% or greater, 90% or greater, or 100% or greater. Polyurethane foam-forming compositions may form foams and foam articles having a tensile strength according to DIN EN ISO 1798 of 150 kPa or greater, 250 kPa or greater, 500 kPa or greater, such as in a range of 150 kPa to 500 kPa. Polyurethane foam-forming compositions may form foams and foam articles having a compression stress resistance according to DIN EN ISO 3386-2 of 120 kPa or more, such as in the range of 120 kPa to 180 kPa. Polyurethane foams and articles prepared therefrom may include a blend of FR additives containing a mixture of APP and MC, with or without EG, and that meet or exceed the requirements for industrial standards of flame resistance, including PV 3357 testing and UL 94 (e.g., V1 or better, or V0 or better). The PU foams and foam-forming compositions have a wide formulation window and include compositions that form low density, high resilience polyurethane foams, slabstock polyurethane foams of a conventional resilience, featuring improved flame retardant performance. The flexible polyurethane foams may have improved flame retardant performance. The nature of the foam forming composition may determine low or high resilience foam forming. For example, high resilience foams may result from foam forming compositions having more or exclusively primary hydroxyl groups, such as ethylene oxide (EO) groups, in condensed form, and / or in compositions having, for example, methyl di(phenyl isocyanate) (MDI) in condensed form. Meanwhile, conventional resilience foams may contain, in condensed form, all secondary hydroxyl groups, such as propylene oxide (PO) groups, or, for example, PO / EO mixed feed polyether polyols. The flame resistant flexible polyurethane foam may be used for and / or molded into an article to be used for and / or molded / foamed in place as an engine cover, an engine noise insulator, a fuel injector encapsulant, a side cover, an oil pan cover, an underhood cover, a hood silencer, and a dashboard silencer, which are disposed around or in the vicinity of an engine of an automotive vehicle, to reduce the amount of sound or noise to be transmitted from the engine. In particular, the flame resistant flexible polyurethane foam may be suitably used and / or molded into articles to be used for or molded / foamed in place as spacers or fillers for filling gaps or spaces between the engine and the surrounding devices, or encapsulation of engine parts for attenuating noise and vibration. While formulation components and properties have been disclosed individually, it is envisioned that component elements may be included, excluded, or combined in any manner or subcombination utilizing any of the above concentration ranges and nested subranges therein. Further, that the recited formulation properties may be similarly achieved through various combinations of the recited components within the recited ranges. Examples The following examples are provided to illustrate the embodiments of the invention, but are not intended to limit the scope thereof. Table 1 provides the materials used in the following examples. Table 1: Materials used in the Examples Component Trade name ); 2; Example 1: FR Testing of Polyurethane Foam Formulations PU foam formulations were prepared and tested for stability and FR performance. The comparative examples (denoted “C”) and inventive examples (denoted “I”) were organized in two parts based on different FR additive formulations. Sample formulations were prepared as A and B sides separately by blending formulation components in the proportions specified in Tables 2-5 by speedmixer. FR rating was performed according to the PV3357 standard to analyze flammability by horizontal flame test and drip testing For the horizontal flame test a 230 mm × 200 mm x 13 mm foam sample was contacted with a flame ignition source for 15 second to 5 minutes. A passing result indicates that the exposed area may have burned through, however, the flame does not continue to spread once the ignition source is removed. Regardless of the flame exposure time (15 s and 5 min), the damaged area must not have a diameter greater than 150 mm. For drip testing, a 160 mm × 200 mm x 13mm foam sample is clamped in a horizontal position and position the ignition source at 45° relative to the specimen in such a way that the drops can fall onto a cotton ball positioned below the area exposed to the flame. The flame height was controlled such that the flame penetrates the component by 10 mm. A cotton plug of about 10 ±5 g is distributed inside an open cylinder with an inside diameter of 100 mm and loaded for 1 min using a 5-kg round plunger. After the load is removed, the distance between the lower edge of the specimen subjected to flame exposure and the upper edge of the cotton ball is approx. 140 mm. A passing result indicates that dripping material was unable to ignite the cotton. Testing results are shown in Tables 2-5. Table 2: Formulations and PV3357 results for Example 1 CE1 CE2 0

[0002] Table 3: Formulations and PV3357 results for Example 1 IE1 IE2 0 Table 4: Formulations and PV3357 results for Example 1 CE3 CE4 0 CE1 and CE2 demonstrate that the addition of 15 wt% of APP or 15 wt% of CC to the isocyanate-reactive component, respectively, does not pass PV3357 specifications. IE1 and IE2 demonstrate the synergy between APP and CC at a ratio of 80 / 20 for various concentrations by passing scores for PV3357 testing. However, CE3 and CE4 demonstrate that lower amounts of APP / CC were unable to pass PV3357 testing. Example 2: Formulations containing expandable graphite PU foam formulations were prepared and tested for stability and FR performance substantially as described above in Example 1, and various combinations with expandable graphite (EG) were surveyed. For UL-94 testing, PU foam formulations were prepared in metal mold at 13 mm thickness and cut to 0.5 inch width and ≥ 10 cm dimensions. Samples were tested pursuant to UL-94 vertical burn protocol and performance was categorized in appropriate category: V0 (best performance), V1, V2, and fail (fail meant the sample burns all the way to the clamp during and / or post the flame exposure). Formulations and results are shown in Tables 5-10. Table 5: Formulations and UL94 results for Example 2 CE6 CE7 6 5 il Table 6: Formulations and UL94 results for Example 2 IE3 IE4 6 5 ss CE8 l Table 8: Formulations and UL94 results for Example 2 CE9 IE5 6 5 ss Table 9: Formulations and UL94 results for Example 2 CE10 CE11 5 l Comparative examples CE6 and CE7 demonstrate, respectively, that the addition of 15 parts of EG or 15 parts of APP / CC (13 parts of APP and 2 parts of CC) to the polyol are not sufficient to produce a PU foam classified as V0, according to the UL94 norm. In contrast, IE3 and IE4 show the synergistic effect of the combination of EG / APP / CC, passing the UL94 V0 classification. In IE3, the concentrations EG, APP and CC are respectively 33wt%, 53wt%, 13wt% based on total weight of EG / APP / CC. In IE4, the concentrations of EG, APP and CC are respectively 86wt%, 10wt%, 2.6wt% based on total weight of EG / APP / CC. CE8 show the limit of the concentrations and relative ratios between the fillers, needed in the formulation to be classified as V0. In CE8, EG is at 22wt%, APP at 63wt% and 16wt% based on total weight of EG / APP / CC. CE9 demonstrates the addition of 10 parts of EG generates a PU foam that does not pass the V0 classification. IE5 shows the synergy of the three components adding a maximum of fillers of 10 parts on the polyol side to achieve a passing UL94 V0 rating, with a concentration of 87 wt% of EG, 10% of APP and 3 wt% of CC based on the total weight of the FR additive component. CE10 and CE11 demonstrate that the replacement of CC with a filler, ATH, does not allow to pass the V0 classification. While the foregoing is directed to exemplary embodiments, other and further embodiments may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

Claims 1. A polyurethane foam composition comprising a polymer matrix prepared by curing a reaction mixture comprising: an isocyanate-reactive component including: one or more polyether polyols having a hydroxyl number from 25 to 100 mg KOH / g, as determined in accordance with ASTM D4274, and having from two to eight hydroxyl groups per molecule; one or more hydroxyl-terminated prepolymers; an FR additive component comprising an ammonium polyphosphate and an alkaline earth metal carbonate in a weight ratio of from 1.3:1 to 6.5:1, and present at a percent by weight of the isocyanate-reactive component (wt%) ranging from 6 wt% to 50 wt%; and an isocyanate component including one or more polyisocyanates.

2. The composition of claim 1, wherein the isocyanate-reactive component further comprises an expandable graphite.

3. The composition of claim 1, wherein the metal carbonate comprises one or more selected from calcium carbonate and magnesium carbonate.

4. The composition of claim 1, wherein the polyether polyol comprises: at least one high molecular weight polyether polyol having a functionality of 2.5 to 3.5 and a number average molecular weight of 3000 Da or more; and at least one low molecular weight polyether polyol having a functionality of 2.5 to 3.5 and a number average molecular weight of 3000 Da or less.

5. The composition of claim 2, wherein the FR additive component comprises APP, MC and EG at an (APP+MC):EG weight ratio ranging from 0.1:1 to 3:1 and is present at a percent by weight of the isocyanate-reactive component (wt%) ranging from 6 wt% to 50 wt%.

6. The composition of any one of claim 1 to 5, wherein the hydroxyl number of one or more polyether polyols is from 30 to 40 mg KOH / g.

7. The composition of any one of claim 1 to 6, wherein the foam forming composition has an isocyanate index from 50 to 150.

8. The composition of any one of claims 1 to 7, wherein the flexible polyurethane foam has a density as determined in accordance with ISO 845 ranging from 150 kg / m3to 300 kg / m3.

9. The composition of any one of claim 1 to 9, wherein the polyurethane foam passes the requirements for PV3357 flame resistance.

10. The composition of any one of claim 1 to 9, wherein the polyurethane foam has a UL94 rating of V0.

11. An engine cover for an automobile comprising the polyurethane foam of claims 1 or 5.

12. A two-component polyurethane composition comprising: an isocyanate-reactive component including: one or more polyether polyols having a hydroxyl number from 25 to 100 mg KOH / g, as determined in accordance with ASTM D4274, and having from two to eight hydroxyl groups per molecule; one or more hydroxyl-terminated prepolymers; an additive component including ammonium polyphosphate and alkaline earth metal carbonate in a weight ratio of from 1.3:1 to 6.5:1, the additive component being present in amount from 6 part by weight to 50 parts by weight, based on 100 parts by weight of the polyol component; and an isocyanate component including one or more polyisocyanates.

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