Polyurethane resin for fiber-reinforced composites

Abstract

Compositions may contain a composite formed by the combination of: an isocyanate component; an isocyanate-reactive component containing: one or more polyether polyols; a catalyst package containing one or more trimerization catalysts and one or more blocked gel catalysts; a flame retardant additive; and a reinforcement material that is present in at least one of the isocyanate component, the isocyanate-reactive component, or provided as a third component; wherein the molar ratio of NCO groups to NCO-reactive groups is in the range of 1.3 to 2.5; and the composite has a UL 94 rating of V1 or better. Methods may include preparing a composite by combining: an isocyanate component; an isocyanate-reactive component containing one or more polyether polyols; a catalyst package containing trimerization catalysts and blocked gel catalysts, a flame retardant additive and contacting the polyurethane-forming composition with a reinforcement material; and generating a polyurethane composite.

Description

[0001] POLYURETHANE RESIN FOR FIBER-REINFORCED COMPOSITES

[0002] FIELD

[0003] Embodiments relate to flame resistant polyurethane (PU) compositions containing fractions of polyisocyanurates that generate compact resin composites having good mechanical properties.

[0004] BACKGROUND

[0005] Fiber-reinforced composites represent a category of materials produced from two or more constituent materials. Composites based on polyurethane (PU) as the thermoset polymeric resin, with fiber reinforcement such as glass fiber, ceramic fiber, or carbon fiber, are of commercial interest as they combine high-strength, high-modulus performance with light weight, fast cycle times / line speeds, and toughness. Composite manufacture may be achieved by a number of processes, including pultrusion, infusion, filament winding, and the like. In most techniques, a PU composition is generated from a two-component formulation that is reacted in presence of reinforcing fibers to generate a supported organic resin matrix. For example, during pultrusion, fibers are impregnated with the resin, and then forced through a hot die, cured, shaped, and continuously pulled to produce a composite article from the die.

[0006] In addition to structural concerns, composite materials exposed to extreme temperatures or open flames may also be required to meet various regulatory standards to minimize safety hazards. Industrial standards typically determine burning behavior resulting from surface and edge flame exposure, measuring the response of a material upon exposure to an ignition source. For most standards, including Underwriters' Laboratories Standard 94 (UL 94) rating system, PU composites must not continue to burn once contacted with an ignition source (i.e., be selfextinguishing) or produce dripping flames. While various flame retardant / resistance (FR) additives are included in PU formulations to comply with regulatory requirements, popular solutions such as melamine and halogen-based compounds can affect the mix viscosities, processing, color, performance, safe handling and quality of PU formulations and composites over time. Further, chemical FR additives may be volatile and / or function as plasticizers that can affect mechanical performance and present hazards in terms of environmental and health safety.

[0007] Summary

[0008] In an aspect, embodiments disclosed herein are directed to compositions containing a composite formed by the combination of: an isocyanate component; an isocyanate-reactive component containing: one or more polyether polyols; a catalyst package containing one or more trimerization catalysts and one or more blocked gel catalysts; and a reinforcement material that is present in at least one of the isocyanate component, the isocyanate-reactive component, or provided as a third component; wherein the molar ratio of NCO groups to NCO-reactive groups is in the range of 1.3 to 2.5; and wherein the composite has a UL 94 rating of VI or better.

[0009] In another aspect, embodiments disclosed herein are directed to methods of preparing a composite containing: preparing a polyurethane-forming composition by combining: an isocyanate component; an isocyanate-reactive component containing: one or more polyether polyols; a catalyst package containing one or more trimerization catalysts and one or more blocked gel catalysts, wherein the molar ratio of NCO groups to NCO-reactive groups is in the range of 1.3 to 2.5; and contacting the polyurethane-forming composition with a reinforcement material; and generating a polyurethane composite by allowing the polyurethane-forming composition to cure in the presence of the reinforcement material.

[0010] Detailed Description

[0011] Embodiments relate to flame resistant polyurethane (PU) compositions containing fractions of polyisocyanurates that generate compact resin composites having good mechanical properties. PU compositions may include one or more flame resistance (FR) additives and a catalyst package for promoting polyisocyanurate formation. Catalyst packages disclosed herein may include a mixture of trimerization catalyst and a blocked gelling catalyst that initiate isocyanurate formation at excess of the amount of NCO groups to the amount of NCO-reactive groups(e.g., molar ratio ranging from 1.3 to 2.5), and reduce the amount of FR additive required for FR performance. Methods may include reacting generating PU composites having a UL-94 vertical burn performance of V2 or better at sample thickness of 10 mm or lower.

[0012] To meet demands of safety, PU compositions and fiber-reinforced composites are formulated with various FR additives, which increase the ability of the material to resist combustion and self-extinguish. However, the inclusion of FR additives can have a number of unintended effects. For example, liquid FR additives are often volatile and can function as plasticizers that reduce modulus and lower glass transition temperatures, while solid FR additives can increase the mix viscosity of a PU-forming mixture reducing fiber wetting and impregnation.

[0013] PU compositions and composites disclosed herein may provide materials containing a fraction of polyisocyanurate generated by the trimerization of isocyanate molecules that provide a synergistic effect when combined with FR additives, decreasing the amount of FR additive. PU compositions disclosed herein may generate a non-foamed (compact) resin, which may be used to generate reinforced fiber composites having effective performance under industrial standards such as UL 94. Further, the presence of polyisocyanurates in the polymer matrix appears to reduce the plasticizing effect of FR additives that negatively impact mechanical properties such as glass transition temperature (or softening temperature), tensile modulus, and flexural modulus.

[0014] PU compositions and composites disclosed herein may be used in a number of structural and functional applications, particularly where flame resistance is preferred, including such as utility poles, utility crossarms, cable trays and racks, transmission cable cores, fenestrations, curtain walls, railway and train interiors, aircraft interiors, spacecraft components, solar panel frames, wind blade components, shelving, RV and trailer components, electric vehicle battery covers, EV battery assembly or isolation parts, transmission mounting systems, vehicle crossmembers, structural components in vehicle seatbacks and composite decking, and the like.

[0015] PU 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 PU and / or PU composite. PU compositions may also include one or more reinforcement materials and / or fillers added to the isocyanate (B) and / or isocyanate-reactive components (A), or as a third component (C) added during mixing.

[0016] A. Isocyanate-reactive component

[0017] The isocyanate-reactive component (or A-side) may contain of one or more of polyether polyols, polyester polyols, polyol dispersions, modified polyols, FR additives, internal mold release agents, a catalyst package, 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%.

[0018] Isocyanate-reactive components may include one or more polyether polyols and in some cases, may include a polyol blend containing two 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. Suitable starter compounds may include molecules having 1 to 8 hydroxyl groups per molecule, such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, 1,4-butanediol, 1,6-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 poly ethers formed from copolymers of alkylene oxides, including block copolymers and polyethers “capped” with hydroxyethyl and / or hydroxypropyl oligomers or polymers.

[0019] In some cases, isocyanate-reactive component may include a single or combination of different hydroxy number (OH#) polyether polyols. These polyether polyols may have an OH# according to ASTM D4274 ranging from 400 mg KOH / g to 2000 mg KOH / g, or 500 mg KOH / g to 1900 mg KOH / g, and a functionality ranging from 2 to 5.

[0020] In some cases, the polyether polyols may be capped with oligomers or polymers of ethylene oxide (EO-capped) that modify elongation properties and toughness. EO-capped polyether polyols may have an ethylene oxide (EO) content at a percent by weight (wt%) of 3 wt% to 50 wt%, or 3 wt% to 30 wt%.

[0021] Isocyanate-reactive components disclosed herein may include a total polyether polyol content at a percent by weight (wt%) ranging from 10 wt% to 90 wt%, 10 wt% to 85 wt%, or 20 wt% to 80 wt%.

[0022] 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.

[0023] 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 2 wt% to 50 wt%, from 5 wt% to 50 wt%, or from 5 wt% to 40 wt%. In some cases, isocyanate-reactive components may include 5 wt% to 40 wt% of a polyester polyol based on terephthalic acid. Isocyanate-reactive components may include one or more polyol dispersions in which copolymer polyol particles (CPP) are dispersed in a carrier polyol (e.g., a polyether polyol). Polyol dispersions may be generated by preparing a CPP in the presence of a carrier polyol by the reaction of one or more polyisocyanates containing two or more isocyanate groups with a stoichiometric excess of “seed polyol” (e.g., an isocyanate index of from 0.5 to less than 1.0). Polyisocyanates may include polymeric isocyanates, aromatic isocyanates, or carbodiimide-modified isocyanates as discussed below with respect to the isocyanate component. Seed polyols may include starter compounds discussed above and / or other compounds with nucleophilic groups (e.g., amines, sulfhydryls, etc.) having a functionality of 2 or more. Seed polyol may be added at a percent by weight (wt%) of the polyol dispersion ranging from 1 wt% to 5 w%, or 2 wt% to 4 wt%. CPP may include polycarbamates such as polyisocyanate poly alcohol (PIPA), and other CPP such as polyhydrazodicarbonamide (PHD), styrene acrylonitrile (SAN), polyurea polyols, and the like.

[0024] Carrier polyols may include polyether polyols (e.g., as described above) having two to eight hydroxyl groups and a weight average molecular weight of up to 6000 Da. Examples of suitable carrier polyols may also include EO end-capped polyether polyols having from 3 wt% to 30 wt% of ethylene oxide, and an hydroxyl number of from 45 to 80 mg KOH / g.

[0025] Polyol dispersions may include a solid particle content at a percent by weight (wt%) ranging from 1 wt% to 40 wt%, or 5 wt% to 40 wt%. The particles may be uniformly distributed as a dispersion in a polyol carrier and may have a particle size diameter (PSD), as determined by laser light scattering, of 90%, by volume, of the particles in the dispersion having a maximum PSD of from 0.1 to 10.0 pm (e.g., from 0.2 to 5.0 pm, from 0.2 to 2.5 pm).

[0026] Isocyanate-reactive components may include one or more polyol dispersions at a percent by weight (wt%) ranging from 1 wt% to 50 wt%, or from 5 wt% to 40 wt%.

[0027] Isocyanate-reactive components may include one or more modified polyols, such as halogenated polyols, phosphorylated polyols, or nitrogenated polyols. Suitable modified polyols may include aromatic or aliphatic halogenated alcohols, diols or triols, such as tetrabromophthalic anhydride diols, dibromoneopentyl glycol, tribromoneopentylalcohol (TBNPA), and the like; phosphorylated polyols may include hydroxylated phosphates and hydroxylated phosphonates, such as N,N-bis-(2-hydroxylethyl)aminomethane phosphonic acid diethyl ester,; nitrogenated polyols such as diethanolamine, monoethanolamine, triethanolamine, and the like; and combinations thereof.

[0028] Isocyanate-reactive components may include one or more flame resistance (FR) additives.

[0029] Suitable FR additives may include phosphorus-containing compounds selected from the group of a phosphate, a phosphite, a polyphosphate, a phosphonate, a phosphinate, a biphosphinate, and combinations thereof. Examples of phosphates include tris(chloroethyl)phosphate (TCEP), tricresyl phosphate, tris(chloropropyl)phosphate (TCPP), triethyl phosphate (TEP), triphenyl phosphate, resorcinol bis(diphenyl phosphate), and combinations thereof. Examples of phosphonates include dimethylmethyl phosphonate (DMMP), diethylethyl phosphonate (DEEP), diethyl(hydroxymethyl) phosphonate, , and the like. Examples of phosphinate additives include a metal salt of organic phosphinate such as aluminum methylethylphosphinate, aluminum diethylphosphinate, zinc methylethylphosphinate, and zinc diethylphosphinate. Examples of phosphites include trimethyl phosphite, triphenyl phosphite, dibutyl phosphite, tris(trimethylsilyl) phosphite, triisopropyl phosphite, diethyl phosphite, tris(nonylphenyl) phosphite, dimethyl phosphite, dibenzyl phosphite and triethyl phosphite. Solid FR additives include aluminum trihydrate, antimony trioxide, boron compounds, melamine cyanurate and melamine compounds, solid phosphorous-containing compounds such as ammonium polyphosphates, red phosphorous, and the like. Additionally included are solid compounds containing zinc, graphite, calcium carbonate, silica, and the like.

[0030] Isocyanate-reactive components may include one or more FR additives at a percent by weight (wt%) ranging from 1 wt% to 50 wt%.

[0031] Isocyanate-reactive components may include one or more internal mold release (IMR) agents in at least one of the isocyanate component or the isocyanate reactive component. IMR agents may include branched fatty acid esters, alcohol phosphate (neutral and un-neutralized), ethyl lactate, silicones, and the like. IMR agents may include esters prepared from the reaction of a polyol having two or more hydroxyl groups with one or more equivalents of a fatty acid (e.g., monoester, diester, triester, etc.). IMR agents may have the general formula of R](0H)n- X(OC=OR2)X, where R1is a branched (i.e., containing one or more secondary and / or tertiary carbons) C 3 to CIO carbon chain polyol having n hydroxy functional groups, such as 2 or more, 3 or more, or in a range of 2 to 8; R2is a linear or branched, saturated or unsaturated C8 to C20 carbon chain; and x is an integer from 1 to 4, or 1 to 3.

[0032] IMR agents disclosed herein may be prepared from the reaction of one or more equivalents of fatty acid(s) with a C3 to CIO polyol such as neopentyl glycol, tri methylol ethane, tri methylol propane, trimethylol butane, di-(trimethylol propane), tri-(trimethylol propane), pentaerythritol, di- (pentaerythritol), tri- (pentaerythritol), and the like. Suitable fatty acids include one or more of C8 to C20 saturated fatty acids such as capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, sebacic acid and the like; C8 to C20 unsaturated fatty acids such as palmitoleic acid, oleic acid, or caproleic acid, synthetic or naturally derived fatty acids such as soya oil acid, lauric acid, cocinic acid, eleostearic acid, tung oil fatty acid, linseed oil fatty acid, castor oil fatty acid, dimers or oligomers thereof, and the like. In some cases, IMR agents may include trimethylolpropane oleate or pentaerythritol oleate.

[0033] IMR agents may be mixed into at least one of the isocyanate component or the isocyanatereactive component at a percent by weight of the respective component (wt%) in an amount ranging from 0.1 wt% to 15 wt%, 0.5 wt% to 12 wt%, or 1 wt% to 10 wt%.

[0034] Isocyanate-reactive components may include one or more catalysts for enhancing polyurethane polymerization to generate the PU composition. Catalysts may be used individually or as a catalyst package containing multiple catalysts, such as gelling catalysts, and trimerization catalysts. Gelling catalysts may favor urethane (gel) reaction, and trimerization catalyst may be utilized to promote the isocyanurate forming reaction in the compositions. In some cases, the catalyst package can also be added as a separate stream into the reaction mixture of isocyanate component and / or isocyanate-reactive component.

[0035] 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.

[0036] Catalysts may include a blocked gelling catalyst (equivalently “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 composition or composite. Ambient temperatures may range 15 °C to 32 °C, where room temperature is often around 23 °C.

[0037] Blocked gelling catalysts can be gelling and / or trimerization types of catalysts in terms of their function in the polymerization process. The blocked gelling catalyst is often a subset of tertiary amine gelling catalysts (e.g., blocked tertiary amines based on 1,8- Diazabicyclo[5.4.0]undec-7-ene (DBU)) 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, POLYCAT®, POLYCAT® SA-102, POLYCAT® SA-8, DABCO® 8154, NTAX™ A-107, NIAX™C-31, NIAX™C-225, JEFFCAT™ ZF-54, JEFFCAT™ LED-204; and mixtures thereof.

[0038] Trimerization catalysts may include any such catalysts known in the art. Examples of trimerization catalysts include quaternary ammonium salts, 2,4,6-(N,N- dimethylaminomethyl)phenols; phenylmethyl amines, N,N',N"-tris(3-dimethylaminopropyl) hexahydro-S-triazine; N,N-dimethylcyclo-hexylamine; 1 ,3,5-tris(N,N-dimethylaminopropyl)-s- hexahydro triazine; [2,4,6-tris (dimethylaminomethyl) phenol]; tris(dialkylaminoalkyl)-s- hexahydrotriazines (such as l,3,5-tris(N,N-dimethylaminopropyl)-s-hexahydrotriazine); potassium acetate, potassium octoate; tetraalkylammonium hydroxides such as tetramethylammonium hydroxide; alkali metal hydroxides such as sodium hydroxide, lithium salts of aliphatic or aromatic mono- or dicarboxylic acids, hydroxyl group containing compounds, and lithium 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-22, DABCO® TMR-18, DABCO® TMR-3, DABCO® TMR-30, DABCO® TMR-7, DABCO® K 2097; DABCO® KI 5, POLYCAT® 41, POLYCAT® 43 and POLYCAT® 46, each from Evonik, Curithane® 52, available from Air Products Company; among other commercially available trimerization catalysts, such as LUPRAGEN® N600, from BASF; TOYOCAT® TRX, TOYOCAT® RX5 and TOYOCAT® TR20 from TriiSO;

[0039] The catalyst or catalyst package may be present in the PU composition at a percent by weight (wt%) ranging from 0.05 wt% to 10 wt%, 0.05 wt% to 7 wt%, or 0.05 wt% to 5 wt%. Catalyst packages 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. In some cases, the catalyst package is a mixture of at least one trimerization catalyst (e.g., phenylmethyl amine, acetate salt) and at least one blocked / latent gelling catalyst (e.g., a blocked DBU) at a percent by weight (wt%) of the isocyanate-reactive component ranging from 0.1 wt% to 5 wt%, where the trimerization catalyst and blocked gelling catalyst form at least 80 wt% of the total catalyst package.

[0040] B. Isocyanate component

[0041] 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 or equal to 2.0, such as in a range of 2.0 to 4.0. PU compositions and PU-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%.

[0042] 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.

[0043] 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%. Isocyanate components may include a polyisocyanate having a percent by weight (wt%) of NCO of 20 wt% or more, or 23 wt% or more, such as in a range of 20 wt% to 80 wt%.

[0044] The isocyanate component may include on or more of aliphatic polyisocyanate, cycloaliphatic polyisocyanate, arylaliphatic 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-l-methyl-l-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.

[0045] 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) in a range of from 0.3 to 4, 0.4 to 3 or 0.4 to 2.

[0046] Examples of commercial isocyanates include, but are not limited to, poly isocyanates under the trade names VORANATE™, PAPI™ , VORATRON™, VORAFORCE™, and ISONATE™, all of which are available from The Dow Chemical Company.

[0047] PU compositions may be generated by combining an isocyanate component with an isocyanate-reactive component at an isocyanate index of 1.3 to 2.5 (a moderate excess to promote isocyanurate formation), calculated as the molar ratio of NCO groups to NCO-reactive groups present in the combined isocyanate and isocyanate-reactive components.

[0048] To generate composites, PU compositions may include one or more reinforcement materials including short or long fibrous materials such as glass fibers, carbon nanotubes, carbon fibers, short polyester fibers, natural fibers, aramid fibers, nylon fibers, basalt fibers, boron fibers, silicon carbide fibers, asbestos fibers, whiskers, metal fibers, surface-functionalized derivatives of thereof, and the like.

[0049] Reinforcement materials and / or fillers may be surface functionalized with a treatment agent to modify hydrophobicity or hydrophilicity. Surface modification may include covalent and ionic attachment chemistries to attach functional groups, such as alkyl chains, siloxane, hydroxyl groups, amines, thiols, isocyanate, epoxies, acrylates, aromatics, hydrosilyl (i.e., SiH), and the like. Treatment agents may vary depending on the nature of the filler or inorganic reinforcement material. For example, silica surfaces may be modified with a silane treating agent to incorporate functional groups that react with, or modify the compatibility of, the filler the PU formulation. PU composites may be generated by contacting a PU composition with one or more reinforcement materials and / or fillers that may be added at a percent by weight (wt%) of the PU composition ranging from 10 wt% to 90 wt%, or 25 wt% to 90 wt%, or 50 wt% to 90 wt%, or 50 wt% to 90 wt%. For example, the amount of PU composition as wt% of the composite may range from 10 wt% to 50 wt% and the reinforcement material and / or filler may be 50 wt% to 90 wt%.

[0050] In some cases, reinforcement material and / or 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. In some cases, articles may be formed from PU compositions, by combining isocyanate and isocyanate-reactive components, dispensing the combined mixture onto a reinforcement material, and processing the resulting composite by a suitable process (e.g., pultrusion, infusion, filament winding, molding, etc.).

[0051] PU compositions disclosed herein may be dense and free of foam to minimize the presence of defects in the final PU composite. PU compositions may be substantially free of blowing agents and may include additives such as moisture scavengers and / or defoamers. PU compositions may include one or more silicone or organic defoamers added at a percent by weight (wt%) of the polyurethane composition in a range of 0.05 wt% to 5 wt%, 0.1 wt% to 1.5 wt%, or 0.1 wt% to 1 wt%.

[0052] The isocyanate component and / or isocyanate-reactive component may also contain one or more additives including surfactants, emulsifiers, rheology modifiers, bio-based molecules, antistatic additive, solid powder(s) and filler(s), anti-freeze additives, odor masking molecules, acrylates, methacrylates, dimethacrylates, radical initiators, crosslinkers, plasticizers, fillers, smoke suppressants, fragrances, dyes, colorants, pigments, preservatives, odor masks, secondary radical stabilizers / activators (such as N,N,4-trimethylaniline), biocides, antioxidants, UV stabilizers, antistatic agents, moisture scavengers, thixotropic agents, adhesion promoters, and the like.

[0053] C. Method of Preparation

[0054] PU compositions disclosed herein may be used to prepare a composite, such as an article or part. Composite formation may include generating a PU-forming composition by combining an isocyanate component and an isocyanate-reactive component to form a mixture by a suitable method (e.g., mixing, injection), which is then used in any suitable process for developing articles and composites, including molding, injection, vacuum infusion, pultrusion, and the like. In some cases, composite part production includes contacting or injecting a PU-forming composition with a reinforcement material, e.g., by vacuum assisted resin transfer molding (VARTM) and / or resin

[0055] - I I - transfer molding (RTM). In other cases, methods of preparing composite articles may include disposing a PU-forming composition on a substrate, into a mold, or by extrusion through a die chamber, followed by curing to generate a composite article.

[0056] PU compositions may produce articles and composites having excellent mechanical properties and a FR performance of ASTM E84, ASTM D635, ASTM El 19, UL94 V vertical bum test, UL94 HB horizontal bum test, UL94 5V, UL 2596, or UL94 VTM Vertical Thin Material test. In some cases, PU composites may have a UL 94 vertical burn rating at a thickness of <10 mm of V2 or better, or VI or better.

[0057] Articles and composites may also be used for a number of applications, including utility poles, fenestrations, data center containment, cable racks, decking, automotives, electric vehicle (EV) battery and its assembly parts such as tray(s), lid(s), plate(s), stmctural member(s), and wall(s), stationary energy storage devices and battery packs, seawalls, wind generator blades, wind generator nacelle housings, watercraft propeller blades, rebars, ladders, cable trays, hulls, interior and exterior automobile decorative parts, automobile bodies, radomes, machinery stmctural members, decorative parts and stmctural members for architectures and bridges, and the like.

[0058] 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.

[0059] Examples

[0060] 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.

[0061]

[0062] Example 1 : Preparation of formulations for PU compositions

[0063] In this example, samples containing polyurethane compositions were formulated by varying the catalyst package and assaying polyurethane reactivity. PU compositions were formulated as shown in Tables 2 and 3.

[0064] PU compositions were prepared by weighing formulation components on an analytical balance and combining on DAC 600. 1 FVZ-K speedmixer. The isocyanate component was then added in accordance with the functional group index and combined by speedmixing. The mixture was poured into a mold (12.5 mm x 12.5 mm x 3 mm) and the mold was cured at 160 °C to 165 °C for 45 mins to 60 mins. Typically, to impart fire performance, common non-reactive flame retardants such as TCPP and / or tricresyl phosphate are added to the polyurethane. However, the addition of more and more non-reactive flame retardant has a detrimental effect on Tg and mechanicals.

[0065] Target properties for a PU composition used in composite applications includes a storage modulus of > 1100 MPa at 25 °C and >1000 MPa at 50 °C, along with a neat resin Tg of > 120 °C. The target for UL 94 flame resistance was V0 at 4mm thickness and without losing more than 2.3 wt% of total mass at 200 °C for 20 minutes.

[0066] Property testing was then conducted as follows. Measured properties for the sample formulations are shown in Tables 4 and 5.

[0067] Fire Resistance performance using UL-94 vertical bum test: The solid materials prepared in metal mold and cut to 4 mm thickness with 0.5 inch width and 125 mm length. The material strips were tested with a standard UL-94 vertical burn protocol and performance was categorized in appropriate category as per the UL guidance - V0, VI, V2, and Fail (Fail meant the sample bums all the way to the clamp during and / or post the flame exposure). The desired performance requires V0.

[0068] Glass transition temperature and Storage modulus: Dynamic mechanical analysis (DMA) was performed to obtain glass transition temperature (Tg) with ASTM D5279-21 on an Advanced Rheometric Expansion System (ARES-G2) from TA Instruments equipped with liquid nitrogen environmental control and torsion rectangular fixtures. A rectangular sample was cut from the plaques prepared in metal molds as per the procedure described above at 2 mm thickness and cut to dimensions of 45 mm length, and 12.8 mm width. The sample length was lined up axial to the torsional axis, and the DMA was performed in torsional mode. The temperature was increased from -50 °C to 200 °C at a ramp rate of 3 °C / min. The frequency of testing was 1 Hz at 0.05% torsional strain, with an axial tensile force of 0.098 N applied to keep sample taut, and at a data collection interval of 30 sec per point. The temperature sweep was done twice to ensure complete cure of plaque and the properties from the second sweep was reported. The major output from the characterization identified were the storage modulus in shear modulus (G’), Loss modulus (G”), and the peak of Tan 6 is assigned as the glass transition temperature (Tg). Thermogravimetric analysis to determine the weight retention performance: To measure the weight retention performance of the various PU samples, isothermal TGA was performed. Isothermal TGA was performed at a ramp rate of 20 °C / min from 25 °C to 200 °C. Sample was held at 200 °C isothermally and weight change was monitored. Test was performed under nitrogen gas.

[0069] CE1 was formulated to generate a polyisocyanurate and excluded FR additive. The resulting polymer fails to meet UL94 test, indicating that the presence of isocyanurate in the polymer was not sufficient to meet certain fire test requirements.

[0070] CE2 was formulated to generate a polyurethane with 20 wt% non-halogenated flame retardant in the formulated polyol. The formulations excluded trimerization catalyst and the isocyanate index is 1, which resulted in negligible polyisocyanurate formation. Despite a large amount of flame retardant additive, the polymer failed the UL94 fire test: it also shows the negative impact of the FR additive, which acts as plasticizers, on important polymer properties such as Tg which is lower.

[0071] CE3 was formulated to generate a polyurethane composition containing aromatic polyester polyol and 20wt% non-halogenated flame retardant, while containing no polyisocyanurate. Similar to CE2 the resulting polymer failed the UL94 fire test. CE4 was formulated to generate a polyurethane composition with 20 wt% FR additive , while containing no polyisocyanurate. The FR additive loading was similar to CE2, but using TCPP. UL 94 performance was improved, but mechanical properties were below acceptable levels.

[0072] CE5 was formulated with aromatic polyester polyol and 15wt% non-halogenated flame retardant, but no trimerization catalyst. The resulting polymer failed the UL94 fire test.

[0073] CE6 was formulated to make a polyurethane with 15 wt% polyol dispersion and 15wt% non-halogenated flame retardant, but no trimerization catalyst. The resulting polymer failed the UL94 fire test.

[0074] IE1 was formulated with a trimerization catalyst and an isocyanate index of 1.5 to provide an excess of NCO groups for isocyanurate conversion. The formulation also included 15 wt%, non-halogenated FR additive. The resulting polymer passed the UL94 fire test.

[0075] IE2 was formulated similarly to IE1 with FR additive 2. The resulting polymer passed the UL94 fire test.

[0076] IE3 was formulated to make a trimerized polyurethane similar to IE1, but also included 5 wt% aromatic polyester polyol. The resulting polymer passed the UL94 fire test.

[0077] IE4 was formulated to make a trimerized polyurethane similar to IE3, but with higher amount of aromatic polyester polyol, and smaller amount of FR additive. The resulting polymer passed the UL94 fire test.

[0078] IE5 was formulated to make a trimerized polyurethane that also contains polyol dispersion and 10 wt% of non-halogenated flame retardant polyol. The resulting polymer passed the UL94 fire test.

[0079] IE6 was formulated to make a trimerized polyurethane, similar to IE1 but with higher concentration of trimer catalyst. The resulting polymer passed the UL94 fire test.

[0080] IE7 was formulated to make a trimerized polyurethane similar to IE7, but with a different combination of trimer catalysts. The resulting polymer passed the UL94 fire test.

[0081] The experimental data in this ICD show that trimerized polyurethane alone (CE1) does not confer acceptable flame resistance. Similarly, samples CE2-CE6 containing FR additive, also do not provide sufficient FR performance. However, IE1-IE7 samples including trimerized polyurethane and FR passed UL94 VO, demonstrating their better performance under fire, modulus and Tg. This shows synergy between the use of FR additives and the presence of polyisocyanurate achieves good polymer performance under fire, while using a lower level of FR additive. In sample IE5, despite containing only 3.7 % FR additive, the sample passes. Samples IE1-IE7 also show good polymer properties, such as high modulus and high Tg. Another surprising benefit of PU compositions of the present disclosure is the weight retention when exposed to 200 °C for 20 min, which is attributed to the decrease volatilization of the FR additive from the polyurethane matrix. 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

Claims1. A composition comprising a composite formed by the combination of: an isocyanate component; an isocyanate-reactive component comprising: one or more poly ether polyols; a catalyst package comprising one or more trimerization catalysts and one or more blocked gel catalysts; and a reinforcement material that is present in at least one of the isocyanate component, the isocyanate-reactive component, or provided as a third component. wherein the molar ratio of NCO groups to NCO-reactive groups is in the range of 1.3 to 2.5; and wherein the composite has a UL 94 rating of VI or better.

2. The composition of claim 1, wherein the one or more polyether polyols comprise a polyether polyol having a functionality of 2 to 5 and a hydroxyl number determined according to ASTM D4274-21 ranging from 400 mg KOH / g to 2000 mg KOH / g.

3. The composition of claim 1 , wherein the one or more polyether polyols comprise a mixture of: a polyether polyol having a functionality of 2 to 5 and a hydroxyl number determined according to ASTM D4274-21 ranging from 400 mg KOH / g to 2000 mg KOH / g; and a polyol dispersion; wherein the weight ratio between the polyether polyol and the polyol dispersion is in the range of 0.1: 1 to 10:1.

4. The composition of claim 1 , wherein the one or more polyether polyols comprise a mixture of: a polyether polyol having a functionality of 2 to 5 and a hydroxyl number determined according to ASTM D4274-21 ranging from 400 mg KOH / g to 2000 mg KOH / g; and a polyester polyol as determined according to ASTM D4274-21 ranging from 100 mg KOH / g to 500 mg KOH / g; wherein the weight ratio between the polyether polyol and the polyester is in the range of 0.1 : 1 to 10:

15. The composition of claim 1, wherein the composition further comprises a polyol dispersion comprising copolymer polyol particles dispersed in a carrier polyol, wherein the copolymer polyol particles are present at a percent by weight of the polyol dispersion ranging from 1 wt% to 40 wt%.

6. The composition of claim 1 , wherein the catalyst package comprises: the one or more trimerization catalyst at a percent by weight (wt%) of the isocyanatereactive component ranging from 0.1 wt% to 5 wt%; and the one or more blocked gelling catalysts at a percent by weight (wt%) of the isocyanatereactive component ranging from 0.05 wt% to 2 wt%.

7. The composition of claim 1, wherein the reinforcement material is one or more selected from glass fiber, carbon fiber, basalt fiber, ceramic fiber, aramid fiber, hemp fiber, and boron fiber.

8. The composition of claim 1, wherein the composite has a glass transition temperature according to ASTM D5279-21 of 120 °C or more.

9. The composition of claim 1 , further comprising a flame or fire retardant additive in the isocyanate-reactive component or isocyanate component at a percent by weight (wt%) ranging from 5 to 30.

10. The composition of claim 1 , wherein the trimerization catalyst and blocked gelling catalyst form at least 80 wt% of the total catalyst package.”11. A method of preparing a composite comprising: preparing a polyurethane-forming composition by combining: an isocyanate component; an isocyanate-reactive component comprising: one or more poly ether polyols; a catalyst package comprising one or more trimerization catalysts and one or more blocked gel catalysts, wherein the molar ratio of NCO groups to NCO-reactive groups is in the range of 1.3 to 2.5; andcontacting the polyurethane-forming composition with a reinforcement material; and generating a polyurethane composite by allowing the polyurethane-forming composition to cure in the presence of the reinforcement material.

12. The method of claim 11 , wherein contacting comprises impregnating the reinforcement material with the polyurethane-forming composition.

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