High strength polyurethane foams formulations with metal adhesive properties

Abstract

Polyurethane foams and foam-forming compositions may include : at least one isocyanate component; and at least one isocyanate-reactive composition containing: at least one low molecular weight polyether polyol having an average functionality ranging from 2 to 8 and a hydroxyl equivalent weight in the range of 30 Da to 400 Da; at least one high molecular weight polyether polyol having an average functionality ranging from 2 to 8 and a hydroxyl equivalent weight in the range of 800 Da to 10,000 Da; at least one phosphate ester adhesion additive comprising one or more hydroxyl functional groups; a low molecular weight polyol chain extender; a catalyst package; and at least one blowing agent; wherein an isocyanate index of the foam-forming composition is from 60 to 300 and the foam has a molded foam density of from 300 kg / m3 to 750 kg / m3 according to ASTM D1622-08.

Description

[0001] HIGH STRENGTH POLYURETHANE FOAMS FORMULATIONS WITH METAL ADHESIVE PROPERTIES

[0002] FIELD

[0003] Embodiments relate to polyurethane foam-forming compositions and polyurethane foam compositions having high density and stiffness, and with good adhesion to metal surfaces.

[0004] INTRODUCTION

[0005] Polyurethane foams provide thermal insulation, tunable mechanical properties, and reduction in density and are utilized in various end use applications, including insulation materials, encapsulants / pottants, and support articles. Polyurethane foams are generally formed from reacting an isocyanate and a polyol in die presence of physical and / or chemical blowing agents. High density polyurethane foams (i.e., ranging from 300 kg / m3to 750 kg / m3) are of particular interest in electronics and supporting industries, such as Electric Vehicle (EV) battery pack assembly, given their high modulus, elongation, tensile strength, and low cure temperatures (e.g., 20 °C to 60 °C), even where the materials are utilized in low thickness regions (e.g., 1 mm to 8 mm).

[0006] However, current high density foam formulations lack the adhesion on bare metal surfaces such as aluminum or stainless steel and require various surface pretreatments (e.g., e-coating). Poor adhesion to metal surfaces can produce poor lap shear and adhesive failure during operation, where foam adhesion fails at the bond line, leaving minimal residue on one of the adhered substrates. Adhesive failure is associated with poor performance, and deemed unreliable for many applications. Improvements in adhesive performance could increase assembly strength, while also reducing overall metal substrate weight by reducing or eliminating the need for primer coatings.

[0007] SUMMARY

[0008] In an aspect, aspects of the present disclosure are directed to polyurethane foams and foamforming compositions, containing: (a) at least one isocyanate component; and (b) at least one isocyanate-reactive composition containing: (i) at least one low molecular weight poly ether polyol having an average functionality ranging from 2 to 8 and a hydroxyl equivalent weight in the range of 30 Da to 400 Da; (ii) at least one high molecular weight polyether polyol having an average functionality ranging from 2 to 8 and a hydroxyl equivalent weight in the range of 800 Da to 10,000 Da; (iii) at least one phosphate ester adhesion additive comprising one or more hydroxyl functional groups; (iv) a low molecular weight polyol chain extender; (v) a catalyst package; and (vi) at least one blowing agent; wherein an isocyanate index of the foam-forming composition is from 60 to 300

[0009] - 1 -

[0010] SUBSTITUTE SHEET (RULE 26) and the foam has a molded foam density of from 300 kg / m3to 750 kg / m3according to ASTM DI 622- 08.

[0011] In another aspect embodiments of the present disclosure are directed to foamed articles prepared from foam-forming compositions, containing: (a) at least one isocyanate component; and (b) at least one isocyanate-reactive composition containing: (i) at least one low molecular weight polyether polyol having an average functionality ranging from 2 to 8 and a hydroxyl equivalent weight in the range of 30 Da to 400 Da; (ii) at least one high molecular weight polyether polyol having an average functionality ranging from 2 to 8 and a hydroxyl equivalent weight in the range of 800 Da to 10,000 Da; (iii) at least one phosphate ester adhesion additive comprising one or more hydroxyl functional groups; (iv) a low molecular weight polyol chain extender; (v) a catalyst package; and (vi) at least one blowing agent; wherein an isocyanate index of the foam-forming composition is from 60 to 300 and the foam has a molded foam density of from 300 kg / m3to 750 kg / m3according to ASTM D1622-08. In some cases, the foamed articles may have a tensile strength according to ASTM D1708- 06a is >10 MPa.

[0012] In another aspect, embodiments may also include multilayer articles containing foamed article having a thickness of > 1 mm and prepared from a foam-forming compositions, containing: (a) at least one isocyanate component; and (b) at least one isocyanate-reactive composition containing: (i) at least one low molecular' weight polyether polyol having an average functionality ranging from 2 to 8 and a hydroxyl equivalent weight in the range of 30 Da to 400 Da; (ii) at least one high molecular weight polyether polyol having an average functionality ranging from 2 to 8 and a hydroxyl equivalent weight in the range of 800 Da to 10,000 Da; (iii) at least one phosphate ester adhesion additive comprising one or more hydroxyl functional groups; (iv) a low molecular weight polyol chain extender; (v) a catalyst package; and (vi) at least one blowing agent; wherein an isocyanate index of the foam-forming composition is from 60 to 300 and the foam has a molded foam density of from 300 kg / m3to 750 kg / m3according to ASTM DI 622-08; where the foam-forming compositions is then emplaced on a high surface energy substrate having a surface energy of 100 dynes / cm or greater.

[0013] DETAILED DESCRIPTION

[0014] Embodiments relate to polyurethane foam-forming compositions and polyurethane foam compositions having high density and stiffness, and with good adhesion to metal surfaces. Polyurethane foams are produced by reacting an isocyanate component with an isocyanate-reactive component containing a mixture of high and low molecular weight (MW) polyether polyols, and an phosphate ester-based adhesion additive. High MW polyether polyols may also include at least one high MW polyether polyol capped with ethylene oxide. Polyurethane foams may have good mechanical properties, particularly when cured at a low thickness (1 mm to 8 mm), and good adhesion to metal surfaces. As used herein, “high density” foamed polyurethane compositions may have a density according to ASTM DI 622-08 in the range of 300 kg / m3to 750 kg / m3, or 300 kg / m3to 700 kg / m3, or 350 kg / m3to 700 kg / m3.

[0015] Unless otherwise specified, all molecular weights in this specification are listed as number average molecular weight. Polyurethane foam compositions disclosed herein may include an adhesion additive that promotes superior adhesion on high surface energy substrates, particularly uncoated or bare metal substrates. High surface energy substrates disclosed herein include metals such as aluminum, steel or alloys, zinc, and the like, non-metals, including glass, polar polymers such as epoxy, polyurethane, or polyester, coated materials such as epoxy-coated aluminum, polyacrylate-coated aluminum, polyester liner-covered aluminum, and the like. Table 1 includes additional examples of suitable high energy substrates. High surface energy substrates in the context of automotive and EV applications include surfaces of battery components (e.g.. battery pack or cell frame), prismatic or pouch cell-based batteries, cylindrical cell batteries, substrate packs, thermal management plates, and other surfaces. As used herein, “high surface energy substrate” refers to substrates having a surface energy of 100 dynes / cm or greater. High surface energy substrates from the list above also include alloys, doped and / or coated substrates, contiguous or mosaic multi-substrate surfaces, and the like having different elements to improve the corrosion resistance, wear performance, hardness, and mechanical or thermal properties. High surface energy substrate may include wrought alloy classes of aluminum doped with several metals and termed to categories into Aluminum series Ixxx to 9xxx depending on type of elements such as Magnesium, Silicone, Copper, Titanium, Zinc, Chromium, Zirconium, and the like of used in Aluminum to create alloy. For automotive and EV battery application specific alloy series pertinent are Ixxx, 3xxx, and 6xxx series. High surface energy substrate may include stainless steel grades such as Austenitic, Ferritic, Martensitic, and combination of those leading to grades such as Duplex stainless steel. The stainless steel substrates may be an alloy with the composition containing different elements for improved performance such as iron, chromium, nickel, manganese, silicone, carbon, phosphorous, sulfur, nitrogen, molybdenum, copper, etc. In some cases, high surface energy metal surfaces may be modified using surface treatments such as flame or plasma or corona or combination of them. In some cases, high surface energy metal surfaces may be modified using surface coating (or finishing) by anodizing, chemical coating, and / or electrochemical deposition.

[0016] Polyurethane (PU) foams and methods of manufacturing foams include the combination of reactive chemical components, such as an isocyanate component with an isocyanate-reactive component, to generate a foam-forming composition. The isocyanate and isocyanate-reactive components may be combined at various stoichiometric ratios that are described by the isocyanate index. The isocyanate index equals the ratio of isocyanate groups to isocyanate-reactive groups (such as OH groups) multiplied by 100. Foam-forming PU compositions disclosed herein may have an isocyanate index ranging from 60 to 250, which is used to generate foam articles having relatively high densities and adhesive properties, while reducing excessive brittleness.

[0017] Foam-forming PU compositions disclosed herein may have delayed foam rise (creaming) compared to standard foaming compositions after dispensing (or spraying), which can increase flow and coverage in mold applications, particularly for molds having large surface area and / or complex geometries. In some cases, foam-forming PU compositions may include isocyanate and isocyanate- reactive components that remain liquid at ambient temperatures for 30 seconds or more after mixing, or for 60 seconds or more after mixing. Ambient temperatures may range 15 °C to 35 °C, where room temperature is often around 23 °C. In some cases, the isocyanate and isocyanate-reactive components remain liquid for 30 seconds or more up to mold temperatures such as up to 60 °C.

[0018] Isocyanate Component

[0019] Polyurethane foam-forming compositions and foams disclosed herein generally include the product obtained from combining a two-component curable composition: an isocyanate component (“A-side”) and an isocyanate-reactive component (“B-side”). During application, the isocyanate and isocyanate-reactive components are mixed, initiating a curing reaction, and forming a polyurethane article or material. PU compositions may also include one or more solid FR additives added to the isocyanate and / or isocyanate-reactive components, or as a third component added during mixing.

[0020] Isocyanate components 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 > 1.5, or > 2.0.

[0021] 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.

[0022] The isocyanate component may include one or more of aliphatic polyisocyanate, cycloaliphatic polyisocyanate, aliphatic polyisocyanate, aromatic polyisocyanate, and the like. Examples of isocyanates include, but are not limited to, methylenediphenyl diisocyanate (MDI, including its isomers); polymeric or oligomeric MDI, or modified 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- 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, partially modified polyisocyanates including uretdione, isocyanurate, carbodiimide, uretonimine, allophanate or biuret structure, and combinations thereof, among others, may be utilized. Examples of commercial isocyanates include, but are not limited to, polyisocyanates under the trade names VORANATE™, VORATRON™, PAPI™, VORAFORCE™ and ISONATE™ available from Dow Chemical Company.

[0023] 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 > 100 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 NCO %, corresponding to the weight percent of NCO groups, remaining after completion of the reaction between isocyanate and isocyanate -reactive compound, which are present in the prepolymer. Isocyanates components disclosed herein may include one or more isocyanate compounds having an NCO content according to ASTM D5155-01 at a percent by weight of > 5 wt%, such as in a range of 5 wt% to 40 wt%, or 10 wt% to 40 wt%, or 12 wt% to 40 wt%.

[0024] The isocyanate component includes at least one isocyanate group containing material (such as a polyisocyanate and / or isocyanate-terminated prepolymer). For example, the isocyanate component includes at least one aromatic polyisocyanate, such as methylene diphenyl diisocyanate (MDI) and / or its oligomers, modified MDI, or polymeric MDI, and / or toluene diisocyanate (TDI). The isocyanate component can include at least 50 wt% (at least 60 wt%, at least 70 wt%, at least 80 wt%, at least 90 wt%, at least 95 wt%, at least 98 wt%, etc.) of one or more polyisocyanates, based on a total weight of the isocyanate component. In some cases, the isocyanate component may include a polyisocyanates a percent by weight (wt%) in a range of 30 wt% to 100 wt%.

[0025] Foam-forming compositions may include an isocyanate component at a percent by weight (wt%) ranging from 30 wt% to 80 wt%, 35 wt% to 75 wt%, 40 wt% to 70 wt%, or 45 wt% to 65 wt%.

[0026] Isocyanate-Reactive Component Isocyanate-reactive component that includes a mixture of one or more of polyether polyol, adhesion additives, low molecular weight polyol chain extender or crosslinkers, blowing agents, catalysts or catalyst systems, and other additives. Polyurethane 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%.

[0027] Isocyanate-reactive components may include a combination of polyether polyols, particularly, (1) low molecular weight (MW) polyether polyols having an average hydroxyl equivalent weight of 450 Da or less, and (2) a high MW poly ether polyol having an average hydroxyl equivalent weight of 800 Da to 10,000 Da. In some cases, the high MW polyether polyols may be ethylene oxide (EO) capped at a percent by weight (wt%) of 3 wt% to 80 wt% of the polyol.

[0028] Polyether polyols may include a polyol functionalized with one or more equivalents of a C3 to C5 alcohol (or mixture of alcohols). Polyether polyols disclosed herein may include products obtained by the polymerization of a cyclic oxide, for example, ethylene oxide (“EO”), propylene oxide (“PO”), butylene oxide (“BO”), tetrahydrofuran, or epichlorohydrin. Polyether polyols may be produced by functionalizing a polyol with a polyether, or polymerizing a cyclic oxide in the presence of a polyol initiator having a functionality ranging from 2 to 8, or 2 to 5. As understood in the ait, the initiator compound, or combination thereof, is generally selected based on desired functionality of the resulting polyether polyol. Polyether polyols may be formed with one or more polyol initiators such as neopentylglycol; 1,2-propylene glycol; trimethylolpropane; pentaerythritol; sorbitol; sucrose; glycerine; alkanediols, such as 1 ,6-hexanediol, 1,4- butanediol, 1,3-butane diol, 2,3-butanediol, 1,3- propanediol, 1,2-propanediol, 1,5-pentanediol, 2-methylpropane-l,3-diol, 1,4-cyclohexane diol, 1,3- cyclohexanedimethanol, 1 ,4-cyclohexanedimethanol, 2,5-hexanediol; ethylene glycol; diethylene glycol; triethylene glycol; 9(l)-hydroxymethyloctadecanol, 1 ,4-bishydroxy methylcyclohexane; hydrogenated bisphenol; 9,9(10, 10)-bishydroxymethyloctadecanol; 1,2,6-hexanetriol; and combinations thereof.

[0029] Isocyanate-reactive components may include one or more low MW polyether polyols having an average functionality of 2 to 8 or 2 to 5, and an average hydroxyl equivalent weight (was indirectly determined according to hydroxyl number measured according to ASTM D4274-23 D where hydroxyl equivalent weight equals to 56100 divided by hydroxyl number) of 450 Da or less, or in the range of 30 Da to 450 Da, or 30 Da to 400 Da. In some cases, low MW polyether polyols may have a number average molecular weight of 450 Da or less, or 350 Da or less. In some cases, the isocyanate- reactive component may include a low MW polyether polyol at a percent by weight ranging from 10 wt% to 90 wt%, or 20 wt% to 90 wt%.

[0030] Isocyanate-reactive components may include one or more high MW polyether polyols having an average functionality in a range of 1 to 8 or 1 to 5, and an average hydroxyl equivalent weight of 800 Da to 10,000 Da, 800 Da to 8,500 Da, or 1,000 Da to 8,000Da. High MW poly ether polyols may be prepared using the chemistries and polyol initiators as discussed above with respect to polyether polyols. High MW poly ether polyols may have a primary hydroxyl content of greater than 40%, greater than 20%, or greater than >60%.

[0031] Further, high MW 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 high MW 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%. In some cases, high MW poly ether polyols may include EO-capped polypropylene oxide having an EO content ranging from 3 wt% to 80 wt% or 3 wt% to 50 wt%, an average functionality ranging from 1 to 8, an average molecular weight ranging from 800 Da to 10,000 Da, and having greater than 40% or greater than 60% primary hydroxyl functional groups.

[0032] Isocyanate-reactive components may include a high MW 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%.

[0033] Polyurethane foam-forming compositions and foams may include one or more adhesion additives that increases adhesive interactions with high surface energy and metal substrates. Adhesion additives may include or be terminated with one or more hydroxyl functional groups that are capable of interacting with isocyanate components in a foam-forming mixture, forming urethane and / or urea bonds. Thus, the adhesion additive can also be termed as reactive adhesion additive or non-leachable adhesion additive. Adhesion additive may include phosphate ester polyols prepared from phosphoric or polyphosphoric acid and one or more equivalents of a polyol having at least two hydroxyl functional groups, or a hydroxyl group functionality of 1 to 8. For example, polyols may include one or more of the polyol initiators above. Polyphosphoric acids described herein may have an acid number according to ASTM D664 of 700 or more, 850 or more.

[0034] Adhesion additives may also include a prepolymer prepared from the reaction of a phosphate ester polyol and an aromatic isocyanate, including any of those listed above such as MDI, having an isocyanate functionality of 1 to 5, and / or an isocyanate content of less than or equal to 40%, or less than or equal to 35%.

[0035] Adhesion additives may have a phosphoric acid content as a percent hy weight (wt%) of less than 7 wt%, less than 5 wt%, or in a range from 0.1 wt% to 5 wt%, or 0.3 wt% to 5 wt%. In some cases, the adhesion additives may have a hydroxyl number according to ASTM D4274-23 of less than 1000 mg KOH / g or less than 750 mg KOH / g, or in a range from 50 to 500 mg KOH / g. In some cases, the adhesion additive has a viscosity as measured by the method of ASTM D2196 of less than 50,000 cps at 25°C, or less than 40,000 cps at 25°C.

[0036] The adhesion additive may be present in the isocyanate-reactive component at a percent by weight (wt%) ranging from 1 wt% to 15 wt%, 1.0 wt% to 10 wt%, or 1.5 wt% to 10 wt%.

[0037] Isocyanate-reactive components may include one or more catalysts for enhancing polyurethane polymerization to generate the polyurethan foams. 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 composition.

[0038] Gelling catalysts include organometallic compounds, tertiary amines, blocked amines, 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.

[0039] Blowing catalysts may include bis-(2-dimethylaminoethyl) ether, pentamethyldiethylenetriamine, triethylamine, tributyl amine, N,N-dimethylaminopropylamine, 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.

[0040] Trimerization catalysts may include any such catalysts known in the art. Examples of trimcrization catalysts include N,N',N"-tris(3-dimcthylaminopropyl) hcxahydro-S-triazinc; 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® KI 5, POLYCAT® 41, and POLYCAT® 46, each from Evonik, among other commercially available trimerization catalysts.

[0041] 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 or latent at ambient temperatures, and which becomes more catalytically active, such as by dissociation, de-co-ordination, 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 15 °C to 35 °C, where room temperature is often around 23 °C.

[0042] 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 l ,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 composition at a percent by weight (wt%) ranging from 0.1 wt% to 10 wt%, or 1 wt% to 7 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.

[0043] Polyurethane foam-forming compositions and foams may include one or more surfactants, such as silicone -based surfactants, polyether-modified silicone surfactants, and organic-based surfactants. Suitable surfactants include silicone polyether surfactants, polysiloxane polyoxylalkylene block copolymers, organic surfactants containing polyoxyethylenepolyoxybutylene block copolymers, and the like. Other surfactants include polyethylene glycol ethers of long-chain alcohols, tertiary amine or alkanolamine salts of long-chain allyl acid sulfate esters, alkylsulfonic esters, alkyl arylsulfonic acids, and combinations thereof. Some commercially available surfactants useful in the isocyanate-reactive composition include VORASURF™ DC 193, VORASURF™ 504, TEGOSTAB® B8418, and mixtures thereof.

[0044] Isocyanate-reactive components may include one or more silicone surfactants at a percent by weight (wt%) of 0.01 wt% to 5 wt%, 0.01 wt% to 3 wt%, or 0.05 wt% to 2 wt%.

[0045] Isocyanate-reactive components may include one or more low molecular weight polyol chain extenders. Suitable chain extenders are hydroxyl and / or amine functionalized compounds, which also includes compounds generally known as crosslinkers. Chain extenders are compounds that contain two or more isocyanate-reactive groups, such as hydroxyl groups, primary amines, or secondary amines. Examples of chain extenders include, but are not limited to, amines, including polyamines; poly hydric alcohols; polyoxy alkylene polyols; polyhydric aromatic compounds, and combinations thereof. Examples of amines include, but are not limited to, diethanolamine, triethanolamine, triisopropanolamine, diisopropanolamine, t-butyltolylenediamine, triaminonane, diethyltolylenediamine, chlorodiaminobenzene, 4,4'-methylene-bis-(3-chloro-2,6-diethylaniline), and combinations thereof. Examples of polyhydric alcohols include, but are not limited to, 1,3 butanediol; 1,4 butanedio; mono-, di-, and tri-ethylene glycols; 1,2,4-butanetriol; dipropylene glycol; glycerin; trimethylolpropane; pentaerythritol, 2,5-dimethyl-l,2,6-hexanetriol; glycerol; and combinations thereof.

[0046] Isocyanate-reactive components may include one or more chain extenders at a percent by weight (wt%) of 0.05 wt% to 10 wt%, 0.2 wt% to 8 wt%, or 0. 5 wt% to 8 wt%. The isocyanate -reactive component may also contain one or more additives including fumed silica, surfactants, thixotropic agents such as poloxamer, viscosity modifiers, fire retardant additives, plasticizers, smoke suppressants, fragrances, reinforcements, dyes, colorants, pigments, preservatives, rheology modifiers, cell stabilizer, inhibitor, odor masks, internal mold release agents, biocides, antioxidants, UV stabilizers, antistatic agents, cell openers, inorganic fillers (including fumed silica, calcium carbonate, aluminum trihydrates, etc), and the like.

[0047] Polyurethane foam-forming compositions and foams may include one or more blowing agents, including water and aqueous fluids; chemical blowing agents, such as hydrocarbons, acids, volatile organics, and the like; and physical blowing agents including gases such as nitrogen, air, carbon dioxide, and the like. Blowing agents may be added to the isocyanate-reactive component at a percent by weight (wt%) ranging from 0.1 wt% to 7 wt%, or 0.1 wt% to 4 wt%. Blowing agents may be added to the isocyanate component and / or during mixing in amount sufficient to provide the mixture with the corresponding weight percentages above.

[0048] In some embodiments, the mole ratio of NCO groups present in the isocyanate component to OH groups present in the isocyanate-reactive component is from 0.8 to 1.6, or from 1.0 to 1.5, or from 1.2 to 1.4. The mix ratio, by weight, for the isocyanate component and isocyanate-reactive component can be determined based upon the desired ratio of NCO groups to OH groups. In some embodiments, the mix ratio, by weight, of the isocyanate component to the isocyanate-reactive component in the final adhesive composition can be from 100:50 to 100:70, or from 100:60 to 100:66.

[0049] In some embodiments, the isocyanate component and isocyanate-reactive component can be made and sold in a package. In some embodiments, the isocyanate component and isocyanatereactive component can each be made and sold individually.

[0050] Polyurethane foam-forming compositions may form foams and foam articles having a density according to ASTM D1622-08 of less than 1 g / mL, or in a range of 300 kg / m3to 750 kg / m3, or 300 kg / m3to 700 kg / m3.

[0051] Polyurethane foam-forming compositions may form foams and foam articles having an elongation at break according to ASTM D1708-06a of 5% or greater, 6% or greater, or 10% or greater.

[0052] Polyurethane foam-forming compositions may form foams and foam articles having a hardness according to ASTM D2240-21 (25 °C) of 50 Shore A or greater, 55 Shore A or greater, or 60 Shore A or greater; or 20 Shore D or greater, 25 Shore D or greater. Polyurethane foam-forming compositions may form foams and foam articles having lap shear adhesion on a high surface energy substrate having a surface energy of 100 dynes / cm or greater that is at least 35% greater, 50% greater, or 60 % greater than a comparative formulation containing no adhesion additive. In some cases, polyurethane foams may have a lap shear adhesion on Al of greater than 1.5 MPa, and / or a lap shear adhesion on stainless steel greater than 4 MPa.

[0053] Polyurethane foam-forming compositions may form foams and foam articles having a cream time of 4 minutes or less.

[0054] Polyurethane foam-forming compositions may form foams and foam articles having a gel time of 10 minutes or less.

[0055] Polyurethane foam-forming compositions may form foams and foam articles having a tack- free time (min) of 15 or less.

[0056] Polyurethane foam-forming compositions may form foams and foam articles having a hardness at 1 hour of 20 Shore D or more or 60 Shore A or more.

[0057] Polyurethane foam-forming compositions may form foams and foam articles having an elastic modulus (E’) of 100 MPa or more.

[0058] Polyurethane foam-forming compositions may form foams and foam articles having an elongation at break (%) of 5 or more.

[0059] Polyurethane foam-forming compositions may form foams and foam articles having an ultimate tensile strength of 10 MPa or more.

[0060] Polyurethane foam-forming compositions may be generated generally by combining the isocyanate component and the isocyanate-reactive component to form a mixture by a suitable method (e.g., static mixing, dynamic mixing, dynamic and static mixing, speedmixing, low pressure mixing, high pressure mixing, overhead mixing with impellers or paint mixers, impingement mixing, and others), and reacting the mixture to form a PU article. Foam-forming compositions, foamed polyurethane articles, multilayer compositions containing one or more foamed polyurethane layers, and methods of this disclosure are useful for a variety of end applications, including use in the assembly of electronic components, battery assemblies, EV manufacture, and the like.

[0061] Foam production may include the steps of: (1) equilibrating the isocyanate component and isocyanate-reactive composition to the mixing; (2) preheating mold surfaces to the molding temperature (generally, for example, between 25 °C to 60 °C) with optional woven and non-woven glass or carbon fibers (e.g., fiber mats, meshes or preforms) placed in the mold; (4) determining the loading quantity of foam forming reaction mixture to achieve the desired overpacking ratio (generally, for example from 150 % to 400 %); (5) mixing the isocyanate component and the isocyanate-reactive composition thoroughly and quickly within 10 s; (6) starting a timer at the beginning of the mixing step (5); (7) transferring the foam forming reaction mixture to the mold immediately or directly injecting the foam forming reaction mixture into the mold; (8) closing the mold (if not a closed mold) and allowing the resulting foam-forming reaction mixture to react to form a PU foam article in the mold (i.e., a molded foam article); (9) opening the mold after reaching the preset demolding time; (10) demolding the foam article; and (11) after completely demolding the foam article, inspecting the foam article by visually observing the foam article for defects such as swelling, shrinkage, bulging, and cracking, if any.

[0062] In some cases, articles may include foamed articles and multilayer articles prepared by mixing an isocyanate component and an isocyanate-reactive component containing at least one phosphate ester adhesion additive containing one or more hydroxyl functional groups, curing the resulting foamforming composition or applying the foam-forming composition to a high energy substrate having a surface energy of 100 dynes / cm or greater. Foamed articles and foam layers in a multilayer article may have a thickness of > 1 mm.

[0063] Processes for preparing a polyurethane foam article can be achieved through any known process techniques in the ait. In general, the polyurethane foam article of the present disclosure may be produced by continuous or discontinuous processes, including the process referred to generally as the reaction injection molding (RIM) process or casting molding process with the foaming reaction and subsequent curing being carried out in molds.

[0064] The mixing of the components of the foam-forming composition can be earned out at a temperature of from 5 °C to 80 °C, or 10 °C to 60 °C, or 15 °C to 50 °C. The molding of polyurethane foam articles can be performed at a mold temperature range from 20 °C to 80 °C, 30 °C to 70 °C, or 35 °C to 60 °C.

[0065] While formulation components and properties have been disclosed individually, it is envisioned that component elements (e.g., compounds in isocyanate or isocyanate -reactive components) 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. The numerical ranges disclosed herein include all values from, and including, the lower and upper value and all values in between. Unless stated to the contrary, implicit from the context, or customary in the art, all parts and percentages are based on weight and all test methods are current as of the filing date of this disclosure. Examples

[0066] The following examples are provided to illustrate the embodiments of the invention, but are not intended to limit the scope thereof. All parts and percentages are by weight unless otherwise indicated. Table 2 lists the materials used to prepare the following examples. Adhesion Additive Synthesis Adhesion Additive 1: Polyether polyol -3 (257.20 g) was charged into a 4-neck round bottom flask equipped with a mechanical stirrer, thermocouple, and nitrogen inlet. Polyphosphoric acid i.e., adhesion additive -3 (5.86 g) was added to the flask I reactor. The mixture was mixed for 10 mins under nitrogen. The mixed solution was heated to 100 °C and the reaction temperature was maintained there for 2 hours. The reaction was cooled down to 60 °C. Then 37.13 g of Methylene diphenyl diisocyanate (Isocyanate -2) was added to the same round bottom flask and maintained at the 60 °C for 3-5 hours with hydroxyl number measurement performed to monitor the completion of the additive formation. Once the hydroxyl number reached < 295, the temperature was cooled down. The adhesion additive -1 was transferred into a plastic jar for further characterization using ASTM D4274-23 for hydroxyl number (265-295 mg KOH / g) and ASTM D2196 (16000 to 24000 mPa.s) at 25 °C for viscosity of the material.

[0067] Adhesion Additive 2: Polyether polyol -3 (257.20 g) was charged into a 4-neck round bottom flask equipped with a mechanical stirrer, thermocouple, and nitrogen inlet. Polyphosphoric acid (adhesion additive -3, 5.86 g) was added to the flask / reactor. The mixture were mixed for 10 mins under nitrogen. The mixed solution was heated to 100 °C and the reaction temperature was maintained for 2 hours and cooled to 40 °C. Adhesion additive -2 was transferred into a plastic jar for further characterization using ASTM D4274-23 for hydroxyl number (345 mg KOH / g + / - 10 %) and ASTM D4440-15 (600 cP + / - 10 %) at 25 °C for viscosity of the material.

[0068] Example 1 : Preparation and characterization of PU foams

[0069] In this example, sample formulations were combined, and foam properties and adhesive strength were analyzed. Comparative (CE) and inventive (IE) samples of foam-forming composition and foams were formulated as shown in Tables 3 and 4.

[0070] Procedure for analyzing foam-forming compositions and molding performance

[0071] Isocyanate-reactive component reagents were weighed on an analytical balance and combined using a speedmixer. Batches are used within two hours of mixing. Water content was measured according to ASTM E1064 and the appropriate amount of water was added to the blend to achieve the desired target. The isocyanate component was then added to the isocyanate-reactive component in the selected ratio (isocyanate index) and the mass of the mixture is recorded. Samples of the foamforming composition were then analyzed as a liquid mixture or decanted into a mold. Following mixing of the foam-forming reaction kinetics were analyzed. Samples were allowed to react and foam properties such as cream time, gel time, and tack-free time were recorded. Timing was initiated as the two components are mixed.

[0072] Mold testing included a mold dimension 20 cm X 15 cm X 0.5 cm, preheated at 40 °C in the oven and mixed resin samples were transferred to the mold while timing for ~30 seconds (from the start of mixing). The mold is then placed in an oven at 40 °C for 30 minutes. The mixed resin sample containing is then measured and the amount of material remaining in the cup after the pour is calculated. Following cure, samples were demolded and dimensions and foam weight were recorded, and the density was maintained at about 600 kg / m3(as per ASTM D1622-08). After demolding (10- 12 minutes), hardness on the surface of the foam sample was measured with a durometer (Shore A scale), and after 30 minutes with a durometer (Shore D scale). If the sample foam breaks or shatters or snaps during the demold or during cutting into microtensile i.e., dog bone shaped samples, it is regarded as too brittle for further testing. The “Testable” foams did not break during the demold or during the cutting for sample shapes for property tests. The remining testable foam samples were left overnight to cure before cutting the samples out for property testing.

[0073] Properties I- IX were tested for the samples as follows:

[0074] Lap Shear Adhesion Strength Test (property #1-11) was determined according to ASTM D 1002- 10 to quantify apparent shear strength of single-lap-joint adhesively bonded metal specimens by tension loading. Tested substrates included aluminum and stainless steel 304. Substrate panels (1 inch X 4 inch) were gently wiped with isopropyl alcohol and assembled for combining 1. Al to Al and II. Stainless steel to stainless steel lap shear measurements. A PTFE spacer of 1 mm thickness was placed between the metal substrates with 0.5 inch overlap. 1 inch wide panels was assembled with removable tapes on bottom. The resin was syringed into the 0.5 inch overlap of the open coupon, which was subsequently closed using a binder clip and placed on the flat end of the binder clip (coupon perpendicular to surface) with removable tape sealing the coupon together. The specimen was placed in oven at 60 °C for 18 hours to achieve complete cure. The clips and tapes were taken out along with the spacers before testing. The density of foam between the plates was confirmed gravimetrically to be 600 kg / m3(+ / - 10%). The lap shear data was analyzed using t-test statistical analysis. Failure during the lap shear tests is categorized as adhesive failure (foam residue on only one side of substrate due to adhesion failure), cohesive failure (foam residue on both side of substrate due to foam failure), or substrate failure (e-coat strip off on foam or break of substrate or bend in the substrate). Cream time (property #111) is the quantification of the time to foam generation measured following the combination of the isocyanate and isocyanate-reactive components by high-pressure mixing and dispensation into a cup. Time to foam bubble generation as well as rise time were judged visually and the time recorded. Gel time (property #IV) was defined as the time between start of mixing and a point at which the material forms a continuous string when poked.

[0075] Tack-free time (property #V) was defined as the time between start of mixing and lack of string formation upon tapping with a tongue depressor.

[0076] Hardness Shore A and / or Shore D at 1 hour (property #VI) was measured after demold by durometer according to ASTM D2240 after 1 hour post pouring resin in a thickness profile of < 1 cm.

[0077] Elastic modulus, E’ (property #VII), elongation at break (property #VIII), and ultimate tensile strength (property #IX) were all obtained using ASTM D1708-06a standard on a microtensile testing machine in which a PU foam sheet of 5 mm thickness was obtained post-mold, aged at room temperature (23 °C) for 2 days, and punched into a dog-bone shape typically deemed as microtensile samples.

[0078] Properties for comparative samples are shown in Tables 5-6, and inventive samples are shown in Tables 7-8. The mechanical properties VII-IX for samples CE2 and CE3 are denoted as “Cannot test” to indicate that foaming and gelling properties (III- V) rendered the samples unsuitable for further testing.

[0079] Comparative formulation CE1 is a high density polyurethane foam having < 1.5 Mpa lap shear’ adhesion on Aluminum 606 IT grade plates and < 5 Mpa on stainless steel 304 i.e., property #1 and II respectively. To enhance adhesion, adhesion additives- 1 and -2 were applied to CE2 and CE3, respectively, at a wt% phosphorous content of 0.08 wt%. Substrate adhesion increased by greater than 100% on Al and greater than 20% on stainless steel for CE2 and CE3, however, foam quality was poor with slow cure, and unsuitable testing mechanical properties (property #VII-IX). Additionally, CE3 containing adhesion additive-3 (polyphosphoric acid) at 0.08 wt% exhibited similar- increases in lap shear strength for Al substrates (-50%), however, this effect was absent when decreased to 0.04% (CE6). The addition of the polyphosphoric acid was also accompanied by a decrease in reaction kinetics, leading to a delay to reach tack-free time (property #III-V) and reduced 1 hr hardness (property #VI). The additional of silane-based adhesion additive-4 in CE5 does not show any improvement in adhesive properties.

[0080] Inventive example IE1 contains the adhesion additive- 1 at 0.08 wt% when used with increased concentration of catalyst showcased improvement in the adhesion on Al of > 90% and >55% on stainless steel. For IE2 containing adhesion additive - 2, there was a > 40% increase in lap shear strength at 0.08 wt%. This value was > 25% higher than use of plain phosphoric acid (CE4), but no similar decrease of reaction kinetics or hardness was observed.

[0081] At the lower concentration of adhesion additive -1 (IE3) and adhesion additive -2 (IE4) to reach a phosphorous content of 0.04 wt% in total foam, there is -40% adhesion improvement on Al substrates compared than the no phosphorous containing CE1 and surprisingly over the same 0.04% phosphorous containing CE6. Thus, the phosphate ester adhesion additive 1 and prepolymer adhesion additive 2 produce superior adhesion on Al substrates (> 40%) as compared to similar concentrations of pure phosphoric acid without any decrease in foam cure rate and hardness. 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 foam-forming composition, comprising:(a) at least one isocyanate component; and(b) at least one isocyanate-reactive composition comprising:(i) at least one low molecular’ weight polyether polyol having an average functionality ranging from 2 to 8 and a hydroxyl equivalent weight in the range of 30 Da to 400 Da;(ii) at least one high molecular weight polyether polyol having an average functionality ranging from 2 to 8 and a hydroxyl equivalent weight in the range of 800 Da to 10,000 Da;(iii) at least one phosphate ester adhesion additive comprising one or more hydroxyl functional groups;(iv) a low molecular weight polyol chain extender;(v) a catalyst package; and(vi) at least one blowing agent; wherein an isocyanate index of the foam-forming composition is from 60 to 300 and the foam has a molded foam density of from 300 kg / m3to 750 kg / m3according to ASTM DI 622-08.

2. The composition of claim 1, wherein the at least one phosphate ester adhesion additive is a phosphate ester prepared from a reaction of (poly)phosphoric acid with one or more equivalents of an alkyl alcohol having an average functionality ranging from 1 to 8 and a hydroxy number according to ASTM 4274-23 of less than 1000 mg KOH / g.

3. The composition of claim 1, wherein the at least one phosphate ester adhesion additive is a phosphate ester prepolymer prepared from a reaction of (poly)phosphoric acid with one or more equivalents of an alkyl alcohol having an average functionality ranging from 1 to 8 and a hydroxy number according to ASTM 4274-23 of less than 1000 mg KOH / g, which is further reacted with an aromatic isocyanate having an isocyanate functionality ranging from 1.5 to 5 and a hydroxy number according to ASTM 4274-23 of less than 500 mg KOH / g.

4. The composition of claim 1, wherein the at least one phosphate ester adhesion additive is present at a percent by weight (wt%) of the isocyanate-reactive component ranging from 1 wt% to 15 wt%.

5. The composition of claim 1, wherein the at least one low molecular weight polyether polyol is present in an amount from 20 wt% to 90 wt%, based on a total weight of the isocyanatereactive component.

6. The composition of claim 1, wherein the at least one high molecular weight poly ether polyol comprises an EO capped high molecular weight polyether polyol comprising 3 wt% to 80 wt% of ethylene oxide.

7. The composition of claim 3, wherein the at least one blowing agent is present at a percent by weight (wt%) of the isocyanate-reactive component ranging from 0.1 wt% to 7 wt%.

8. The composition of claim 1, wherein the foam- forming composition comprises a percent by weight (wt%) the total composition of isocyanate ranging from 30 wt% to 80 wt%.

9. A foamed article prepared from the composition in claim 1.

10. The foamed article of claim 10, wherein the tensile strength according to ASTM D1708-06a is >10 MPa.

11. A multilayer article comprising a foamed article having a thickness of > 1 mm and prepared from the composition in claim 1; and emplaced on a high surface energy substrate having a surface energy of 100 dynes / cm or greater.

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