Thermoactivated polymeric catalyst with adhesion promoting activity

Abstract

Two-component adhesive compositions may include A) an isocyanate-reactive component including one or more vegetable oil polyols having a hydroxyl number according to ASTM D4274-21 in a range of 50 mg KOH / g to 400 mg KOH / , a catalyst complex formed by one or more phosphate ester polyols and one or more tertiary amine catalysts, wherein the ratio of phosphate ester polyol to tertiary amine catalyst ranges from 100:1 to 10:1; and B) an isocyanate component including one or more isocyanate-terminated prepolymers. Methods may include preparing a polyurethane adhesive composition using the two-component adhesive composition that includes forming and applying a curable mixture containing the polyurethane adhesive to a first substrate; contacting the first substrate with a second substrate; and allowing the curable mixture to cure and form an adhesion between the first and second substrates.

Description

[0001] THERMOACTIVATED POLYMERIC CATALYST WITH ADHESION PROMOTING ACTIVITY FIELD

[0002] Embodiments relate to polyurethane adhesive compositions containing a catalyst complex that functions as a latent catalyst while also enhancing adhesion on various surfaces.

[0003] BACKGROUND

[0004] Polyurethane (PU) adhesives are extensively used in applications such as food and non-food packaging, laminating, and as structural adhesives. Polyurethane adhesives are typically prepared by combining a two component system in which an isocyanate component is combined with an isocyanate-reactive component, where various additives such as rheology modifiers, adhesion promoters, fillers, and catalysts tailor various strength and curing properties. In the electric vehicle (EV) battery industry, the curing process and catalyst stability are crucial for product performance. High adhesion values are required at both high and low temperatures, while maintaining long open times and slow gel times.

[0005] Adhesion promoters are often added to PU formulations in various contexts to enhance adhesive compatibility with ranges of surfaces, particularly for automotive applications like EV batery frames. However, adhesion promoters often interact with catalysts and create irregular curing behavior. Negative interactions can affect shelf-life and performance characteristics of the PU composition necessary in the demanding environment of EV battery applications.

[0006] SUMMARY

[0007] In an aspect, embodiments disclosed herein are directed to Two-component adhesive compositions may include A) an isocyanate-reactive component including one or more vegetable oil polyols having a hydroxyl number according to ASTM D4274-21 in a range of 50 mg KOH / g to 400 mg KOH / g, a catalyst complex formed by one or more phosphate ester polyols and one or more tertiary amine catalysts, wherein the ratio of phosphate ester polyol to tertiary amine catalyst ranges from 100:1 to 10:1; and B) an isocyanate component including one or more isocyanate -terminated prepolymers.

[0008] In another aspect, embodiments disclosed herein are directed to methods of preparing a polyurethane adhesive composition, including: forming a curable mixture by combining an isocyanate-reactive component and an isocyanate component, the isocyanate-reactive component including: one or more vegetable oil polyols having a hydroxyl number according to ASTM D4274-21 in a range of 50 mg KOH / g to 400 mg KOH / g, a catalyst complex formed by one or more phosphate ester polyols and one or more tertiary amine catalysts, wherein the ratio of phosphate ester polyol to tertiary amine catalyst ranges from 100:1 to 10:1; and the isocyanate component including one or more isocyanate-terminated prepolymers; applying the curable mixture to a first substrate; contacting the first substrate with a second substrate; and allowing the curable mixture to cure and form an adhesion between the first and second substrates.

[0009] DETAILED DESCRIPTION

[0010] Embodiments relate to polyurethane adhesive compositions with a catalyst complex containing a mixture of phosphate ester polyols and tertiary amine catalysts. Catalyst complexes disclosed herein may tune the catalytic activity of various classes of catalysts, including tertiary amines, to extend curing times, even at elevated temperatures (e.g., 45°C). PU adhesive formulations incorporating a catalyst complex may also enhance adhesion, particularly to high energy and / or metallic surfaces.

[0011] Polyurethane compositions and adhesive formulations disclosed herein may include an adhesion additive that promotes adhesion on substrates, which may include high surface energy substrates such as metals and polar polymers. As used herein, “high surface energy substrate” refers to substrates having a surface energy of 100 dynes / cm or greater, and in some cases 500 dynes / cm or greater (e.g, aluminum at 840 dynes / cm). 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. In some cases, substrates may be uncoated or bare metal substrates, doped and / or coated substrates, contiguous or mosaic multi-substrate surfaces, and the like.

[0012] PU adhesive 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 and isocyanatereactive components are mixed, initiating a curing reaction, and forming a polyurethane adhesive and / or article. PU adhesive compositions may also include a catalyst complex added to the isocyanate-reactive component, or as a third component added during mixing.

[0013] A.) Isocvanate-reactive component

[0014] The isocyanate-reactive component (or A-side) may contain one or more of hydrophobic polyols, catalyst complexes prepared from one or more phosphate ester polyols and one or more tertiary catalysts, rheology modifiers, and other additives.

[0015] PU adhesive compositions may include one or more hydrophobic polyols such as one or more vegetable oil polyols or multi-functional polyether polyols. As used herein, “vegetable oil polyol” refers to vegetable oil-based derivatives of polyols, and oligomers and / or polymers such as polyethers, polyesters, polyurethanes, and mixtures thereof. Vegetable oil polyols may have average hydroxyl group functionality of greater than 1.5, greater than 2.0, or in a range of 2 to 4. In some cases, the vegetable oil polyols include vegetable oil derivatives of a polyol having a hydroxyl number (OH#) according to ASTM D4274-21 in a range of 50 mg KOH / g to 400 mg KOH / g, 100 mg KOH / g to 400 mg KOH / g, or 150 mg KOH / g to 400 mg KOH / g.

[0016] As an example, hydrophobic polyols may include castor oil-modified polyurethane polyol or castor oil-modified poly ether polyols. Hydrophobic polyols may have a density according to ASTM D3574-17 Test A of less than 1 g / mL, or in a range of 0.2 g / mL to 1.0 g / mL, or 0.3 g / mL to 0.9 g / mL.

[0017] Isocyanate-reactive components may include one or more hydrophobic polyols at a percent by weight (wt%) ranging from 10 wt% to 70 wt%, 10 wt% to 60 wt%, or 30 wt% to 60 wt%.

[0018] PU adhesive compositions disclosed herein may include a catalyst complex that modifies the curing rate of the PU and / or improves adhesive to high energy substrates. The catalyst complex may be prepared by reacting the phosphate ester polyol with a tertiary amine catalyst, which is then added to the isocyanate-reactive component. In some cases, the catalyst complex may be formed in situ in the isocyanate -reactive component. The catalyst complex may also be added as a separate stream into the reaction mixture of isocyanate and isocyanate-reactive components in some cases. Catalyst complexes may be prepared by combining one or more phosphate ester polyols with one or more tertiary amines at a mass ratio ranging from 100:1 to 10:1, or 100:1 to 20:1.

[0019] Phosphate ester polyols can be made from the reaction of hydroxyl-terminated compounds and phosphoric acid or polyphosphoric acid. Suitable hydroxyl-terminated compounds include polyester polyols, polycaprolactone polyols, polyether polyols, polycarbonates polyols, natural oil polyols, modified natural oil polyols (e.g., modified by hydroxylation, epoxidation), and mixtures and copolymers thereof. The average OH number for the hydroxyl-terminated compounds can be from 5 to 2000 mg KOH / g, 10 mg KOH / g to 1000 mg KOH / g, or 50 mg KOH / g to 900 mg KOH / g. The average functionality of the hydroxyl-terminated compounds can be from 1.0 to 6.0, or from 1.8 to 4.0, or from 2.0 to 4.0. Average molecular weight of the hydroxyl-terminated compounds can be from 25 to 12,000 g / mol, or from 250 to 6,000 g / mol, or from 350 to 3,000 g / mol.

[0020] In some embodiments, phosphate ester polyols can be made by reaction of hydroxyl-terminated compounds, phosphoric acid or polyphosphoric acid, and a polyisocyanate such as methyl diphenyl diisocyanate. As discussed, suitable isocyanate-terminated prepolymers are the reaction products of a polyisocyanate and an isocyanate-reactive mixture at a stoichiometry ratio (NCO / OH) greater than 1, or between 2 and 6, or between 2.5 and 4.0. The polyisocyanate is selected from aromatic isocyanates, aliphatic isocyanates, and cycloaliphatic isocyanate.

[0021] The isocyanate-reactive component one or more phosphate ester polyols at a percent by weight (wt%) ranging from 2 wt% to 25%, 5 wt% to 20 wt%, or 5 wt% to 15 wt%.

[0022] In addition to the above isocyanate-reactive components, isocyanate-reactive components may include a balance of additional polyol species (including those above) such as polyester polyols (e.g., castor oil multi-functional polyether polyol), polyether polyols, polyether ester polyols, polycarbonate polyols, polyurethane polyols at a percent by weight (wt%) up to 99 wt% or less, or 95 wt% or less, such as in a range of 5 wt% to 95 wt%.

[0023] Tertiary amine catalysts may function as gelling catalysts that promote the urethane (gel) reaction during polyurethane cure. Tertiary amine catalysts may include sterically hindered tertiary amines; a long chain tertiary amines (i.e., amine substituents of at least 6 hydrocarbons); and cyclic and bicyclic tertiary amines. Suitable tertiary amines include dimorpholinodialkyl ether, di((dialkylmorpholino)alkyl)ether such as (di-(2-(3,5-dimethyl-morpholino)ethyl)ether), triethylene diamine, N, N-dimethylcyclohexylamine, N, N-dimethyl piperazine, 4-methoxyethyl morpholine, N-methylmorpholine, N-ethyl morpholine, or mixtures thereof. In some embodiments, tertiary amine catalysts may include N-hydrocarbyl substituted amidines or guanidines and cyclic amidines or cyclic guanidines, such as l,8-diazabicyclo[5.4.0]undec-7-ene (DBU), l,5,7-triazabicyclo[4.4.0]dec-5-ene, diazabicyclo[5.4.0]undec-7-ene, and N-methyl-1,5,7-triazabicyclododecene, and the like.

[0024] The tertiary amine catalyst may be present in the isocyanate-reactive component at a percent by weight (wt%) ranging from 0.001 wt% to 5.0 wt%, from 0.01 wt% to 2.0 wt%, or from 0.02 wt% to 0.5 wt%.

[0025] The catalyst complex may be present in the PU adhesive composition at a percent by weight (wt%) ranging from 0.1 wt% to 10 wt%, or 0.1 wt% to 3 wt%.

[0026] B.) Isocyanate component

[0027] The isocyanate component (or B-side) may contain one or more isocyanate-terminated prepolymers, and other additives such as rheology modifiers or adhesion promoters.

[0028] Isocyanate components may include one or more isocyanate-terminated prepolymers. Isocyanate-terminated prepolymers may be any prepolymer(s) prepared by the reaction of one or more polyols with a stoichiometric excess of one or more polyisocyanates containing two or more isocyanate groups. The polyisocyanates may be aromatic, aliphatic, araliphatic or cycloaliphatic polyisocyanates, or mixtures thereof. Suitable polyisocyanates include toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), tetramethylene-l,4-diisocyanate, cyclohexane -1,4-diisocyanate, hexahydrotolylene diisocyanate, l-methoxyphenyl-2,4-diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenylmethane-2,4'-diisocyanate, 4,4' -biphenylene diisocyanate, 3,3'-dimethoxy-4,4'-diphenyl diisocyanate, and 3,3'-dimethyldiphenylpropane-4,4'-diisocyanate; isomers thereof, or mixtures thereof. Suitable polyisocyanates may have an average isocyanate functionality of 1.9 or more, 2.0 or more, 2.1 or more, or 2.2 or more, and at the same time, 3.5 or less, 3.2 or less, 3.0 or less, or 2.8 or less. The isocyanate-terminated prepolymer may have an isocyanate (NCO) content by weight according to ASTM D5155-19 of 1 wt% or more, 2.7 wt% or more, or 5 wt% or more, and at the same time, 30 wt% or less, 25 wt% or less, or 20 wt% or less.

[0029] The polyols and polyol mixtures used to prepare the isocyanate-terminated prepolymer may include any of those disclosed above and further may include ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentylglycol, bis(hydroxy -methyl) cyclohexanes such as 1,4-bis(hydroxymethyl)cyclohexane, 2-methylpropane-l,3-diol, methylpentanediols, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, and the like. Polyols for preparing the isocyanate-terminated prepolymer may also include oligomers and polymers such as polypropylene glycol, polyester polyols, polyether polyols, and the like. In some cases, polyester polyols may include dimeric acid polyester polyols prepared from the polymerization of a polyol and C13 to C22 dimers of long chain carboxylic acids. Isocyanate-terminated prepolymers may be formed using a catalyst, which may include amine -based catalysts and / or tin-based catalysts. In some cases, the isocyanate-terminated prepolymer may be based on dimer acid polyester polyol and a polyisocyanate such as MDI.

[0030] 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.

[0031] The isocyanate component may include an isocyanate prepolymer at a percent by weight (wt%) up to 95 wt% such as in a range of 5 wt% to 95 wt%, 10 wt% to 95 wt%, or 50 wt% to 95 wt%.

[0032] One or more of the isocyanate component and isocyanate-reactive components may include one or more rheology modifiers to modify the thixotropic properties for different application needs. Rheology modifiers may include colloidal silica, fumed silica, precipitated silica, diatomaceous earths, ground quartz, kaolin, calcined kaolin, wollastonite, hydroxyapatite, calcium carbonate, hydrated alumina, magnesium hydroxide, carbon black, titanium dioxide, aluminum oxide, vermiculite, zinc oxide, mica, talcum, iron oxide, barium sulphate, and the like.

[0033] One or more rheology modifiers may be added to the isocyanate component and / or isocyanate-reactive component (or as a third component upon mixing) to give a total percent by weight (wt%) of the PU adhesive composition of up to 15 wt%, such as in a range of 0.1 wt% to 15 wt%, 0.1 to 10 wt%, or 1 wt% to 10 wt%.

[0034] PU adhesive compositions may include one or more additives provided to the isocyanate component and / or the isocyanate reactive component, including moisture scavengers (e.g., zeolites, molecular sieves, p-toluene sulfonyl isocyanate), adhesion promoters, thixotropic agents, color agents such as dyes or pigments, antioxidants, wetting agents such as surfactants, filler dispersion agents, thickening agents, compatibilizers, anti-settling agents anti-syneresis agents, flame retardants, and / or filler treatment agents (e.g., silanes).

[0035] C. Method of Preparation

[0036] PU adhesive compositions disclosed herein may be achieved by mixing the respective components of the isocyanate component and the isocyanate-reactive component in any sequence and allowing the mixture to cure. Suitable mixing techniques include the use of a Ross PD Mixer (Charles Ross), Myers mixer, FlackTek Speedmixer, butterfly mixer and the like. Various components of the composition could also be mixed using a continuous process.

[0037] In some cases, methods of using the polyurethane adhesive composition include combining an isocyanate-reactive component and an isocyanate component to form a curable mixture, applying the curable mixture to a first substrate, contacting the first substrate with a second substrate; and allowing the curable mixture to cure and form an adhesion between the first and second substrates. The curable mixture can be cured at an ambient temperature (18 °C to 35 °C) for several days (for example, 3 to 10 days). In some cases, the curable mixture can be subjected to pressure or heat (for example, at a temperature of from 30°C to 90°C, for example, from 30°C to 60°C) to speed the curing. The material or type of the substrate to be treated (for example, the first substrate and the second substrate) by the PU adhesive composition is not limited. In an exemplary embodiment, the first substrate can be one or more battery cells and the second substrate can be a cooling plate.

[0038] PU adhesive compositions may be prepared by mixing the isocyanate component and the isocyanate-reactive component at a volume ratio of 1: 1 and an ISO index (also known as NCO / OH molar ratio) from 0.95 to 1.9, or 1.05 to 1.85. In some cases, the volume ratio of isocyanatereactive component to the isocyanate component is in a range of 2: 1 to 5:1.

[0039] Cured PU adhesive compositions may have a density according to ASTM D3574-17 Test A of less than 0.9 g / mL or less than 0.85, such as in a range of 0.1 g / mL to 0.9 g / mL, or 0.1 g / mL to 0.85 g / ml.

[0040] PU adhesive compositions may have a lap shear strength according to ASTM D1002 at seven days of 8 MPa or more, or of 10 MPa or more.

[0041] PU adhesive compositions may have a shear stress open time to surpass 2000 Pa at 45 °C according to ASTM D1002 of at least 1400 seconds, or at least 1500 seconds.

[0042] Described compositions can be used as structural adhesives for automotive applications, including for assembly and support in electric vehicle batteries. PU adhesive compositions may be applied as gap fillers and pastes, such as between a battery module and a cooling plate. Manual or automatic dispensing tools can be used to apply adhesive compositions directly to the target surface to minimize waste. In an embodiment, PU adhesive compositions may be prepared by combining an isocyanate component and an isocyanate-reactive component and applying to a cooling plate or heat sink an automated mix-meter-dispense system, followed by installation of a battery cell, module or pack, or other heat source.

[0043] Additionally, adhesive compositions may be used to form pre-cured articles such as gap pads. In one example, pre -cured articles may be formed by curing a PU adhesive composition at a desired thickness, cutting the article to a desired shape, and then compressed to fix in place as needed. In some cases, cured articles may also help reduce vibration stress for shock dampening. 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.

[0044] EXAMPLES

[0045] 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 1 lists the materials used in the following examples:

[0046] | Table 1: Component chemicals used in the examples ~| Component Description

[0047] Hydrophobic VORATRON™ EG-711; 50 weight percent zeolite powder

[0048] DOW

[0049] Polyol in castor oil

[0050] Phosphate Ester

[0051] MOR-FREE™ 88-138; OH number 295, density 1.3 g / cm3DOW Polyol

[0052] Tertiary Amine

[0053] POLYCAT® DBU; diazabicycloundecene EVONIK Catalyst

[0054] Comparative

[0055] POLYCAT® SA4; latent catalyst based on 1,8- Latent EVONIK diazabicyclo[5.4.0]undec-7-ene

[0056] Catalyst

[0057] Rheology HDK H18; hydrophobically modified fumed silica, density WACKER

[0058] Modifier 2.1 g / cm3

[0059] Isocyanate Voranate M220, isocyanate -terminated prepolymer based on

[0060] DOW

[0061]

[0062] Prepolymer dimer acid polyester polyol and MDI

[0063] Example 1: Polyurethane adhesive formulations

[0064] Polyurethane adhesive formulations were prepared for comparative and inventive examples as shown in Tables 2 and 3. Samples assayed include CE1 (no phosphate ester polyol or tertiary amine catalyst), CE2 (tertiary amine alone), CE3 (comparative latent catalyst), and IE1 and IE2 containing the catalyst complex of the present disclosure at differing ratios. For IE1 and IE2 the catalyst complex was prepared by mixing in ratio 10 / 0.5 and 10 / 0.1 phosphate ester polyol / tertiary amine catalyst.

[0065] Table 2: Sample formulations

[0066] Component Units CE1 CE2 CE3 CE4

[0067] A B A B A B A B A Side

[0068] side side side side side side side side Hydrophobic Polyol % 97.56 - 97.26 - 97.26 - 91.95 - Phosphate Ester

[0069] % - - - - - - 5.75 - Polyol

[0070] Tertiary Amine

[0071] % - - 0.30 - - - - Catalyst

[0072] Rheology Modifier % 2.44 - 2.43 - 2.43 - 2.30 - Comp. Latent

[0073] % - - - - 0.30 - - - Catalyst

[0074] B Side

[0075] Isocyanate

[0076] % - 95.24 - 95.24 - 95.24 - 95.24 Prepolymer

[0077] Rheology Modifier % - 4.76 - 4.76 - 4.76 - 4.76 Total % 100 100 100 100 100 100 100 100 Ratio A / B 4.000 4.013 4.000 4.013

[0078]

[0079] Isocyanate Index 113 113 113 113 Table 3: Sample formulations

[0080] Component Units CE5 IE1 IE2 A Side A side B side A side B side A side B side Hydrophobic Polyol % 86.86 - 91.69 - 88.790 - Phosphate Ester Polyol % 10.85 - 5.73 - 11.09 - Tertiary Amine Catalyst % - - 0.28 - 0.11 - Rheology Modifier % 2.17 - 2.29 - 2.22 - Comp. Latent Catalyst % 0.10 - - - - - B Side

[0081] Isocyanate Prepolymer % - 94.737 - 95.238 - 95.238 Rheology Modifier % - 5.263 - 4.762 - 4.762 Total 100 100 100 100 100 100 Ratio A / B 3.33 3.55 3.34

[0082]

[0083] Isocyanate Index 113 113 113

[0084] Lap Shear Measurement was conducted as follows. Corresponding A and B parts were added to a cup in 1:1 ratio by vol and mixed using a high-speed mixer. Immediately after mixing, the resultant paste material was sandwiched between two aluminum metal plates. Adhesive thickness was 0.26 mm and the area of overlap between the plates was 2.5 cm x 2.5 cm. The samples are then allowed to cure at 23 °C for one week. After curing, the two aluminum plates were loaded into a Instron® Model 5500 S mechanical testing frame equipped with 2.5 kN load cell and separated by pulling at a rate of 5 mm / min in a direction parallel to the plane of adhesion. Peak mechanical load during rupture was recorded for each sample and reported as lap shear strength.

[0085] Shear stress was measured by rheometer Anton Paar MCR 102 with Shear rate 1 s'1and 1 mm of thickness at 45 °C.

[0086] Table 4: Formulation pro perties

[0087] Tested Property Target CE1 CE2 CE3 CE4 Lap Shear Strength (LSS) on 0.01 1.0 0.01 >0.8 MPa - Aluminum at 8 min 70°C curing MPa MPa MPa 1.3 1.5 2.4 0.61 LSS on Aluminum at 4h 80°C curing >5 MPa

[0088] MPa MPa MPa MPa LSS on Aluminum at 7 days and 25 2.7 5.2 6.2

[0089] >7 MPa - °C curing MPa MPa MPa

[0090] Time to surpass

[0091] 2000 Pa >1500 950 500 >1500 Shear Stress - Open time at 45°C

[0092] (the longer, the sec sec sec sec

[0093]

[0094] better)

[0095] Table 5: Formulation properties

[0096]

[0097]

[0098] Tested Property Target CE5 IE1 IE2 Lap Shear Strength (LSS) on Aluminum 3.2 5.8 >0.8 MPa - at 8 min 70°C curing MPa MPa 8.5 5.6 9.3 LSS on Aluminum at 4h 80°C curing >5 MPa

[0099] MPa MPa MPa LSS on Aluminum at 7 days and 25 °C 11.6 7.9 12.7 >7 MPa

[0100] curing MPa MPa MPa Performance after aging of Part A

[0101] LSS on Aluminum at 8min 70°C curing 0.7 5.6 >0.8 MPa - - Part A aged 4 weeks at 40°C MPa MPa LSS on Aluminum at 8min 70°C curing 0.6 5.5 - Part A aged 10 weeks at 40°C MPa MPa LSS on Aluminum at 4h 80°C curing- 8.4 9.4 >5 MPa - Part A aged 4 weeks at 40°C MPa MPa LSS on Aluminum at 4h 80°C curing- 8.5 9.4 Part A aged 10 weeks at 40°C MPa MPa LSS on Aluminum at 7 days and 25 °C 9.1 12.5 >7 MPa - curing- Part A aged 4 weeks at 40°C MPa MPa LSS on Aluminum at 7 days and 25 °C 9.3 12.6 curing- Part A aged 10 weeks at 40°C MPa MPa Time to surpass 2000 1200 1500 >1500 Shear Stress - Open time at 45°C

[0102]

[0103] Pa (longer = better) sec sec sec

[0104] Adhesives used in EV battery applications typically need to have a long open time and exhibit high adhesion. Traditional catalysts and adhesion promoters are affected by highly formulated systems, making more stable systems preferable. CE1 demonstrates that without a catalytic system, curing is either slow (0.01 MPa of LSS in 8 minutes) or results in low adhesion (1.35 MPa after full curing, 2.7 MPa at room temperature). However, an extended open time can be maintained at 45°C, taking over 1500 seconds to exceed 2000 Pa of shear stress.

[0105] CE2 contains a common DBU catalyst. This system had an open time of 950 seconds but relatively low beneficial on the adhesion, particularly regarding the full curing (1.0 MPa of LSS for the fast curing, 1.5 MPa of LSS for the full curing, 5.2 MPa for room temperature curing). This result confirms the importance of adhesion promoter in the adhesive formulation.

[0106] CE3 contains a commercial latent catalyst with an activation temperature between 50 °C to 70°C. This latent catalyst improves adhesion compared to CE1 and CE2 (2.4 MPa of LSS for full curing, 6.2 MPa for room temperature curing), evidencing the significance of thermally activated systems for optimal adhesion. However, the shear stress study indicated a rapid shear increase (500 seconds) at 45°C, which is below the reported activation temperature for the latent catalyst. This suggests that interactions with complex adhesive formulations can alter the performance of the catalyst, complicating adhesive composition design. CE4 lacks a catalyst but includes phosphate ester polyol (Mor-Free 88-138). Without a catalyst, it exhibited curing similar to CE1 (0.01 MPa of LSS in 8 minutes), showing that the phosphate ester polyol does not enhance catalytic or adhesive performance. The long reaction profile corresponds with an extended open time (over 1500 seconds). These findings highlight the necessity of an amine-based catalyst for achieving prompt curing.

[0107] CE5 features a combination of Polycat SA4 and the phosphate ester polyol in a 10 / 0.1 ratio. The initial adhesive showed good adhesion (3.2 MPa of LSS for fast curing, 8.5 MPa for full curing, 11.6 MPa for room temperature curing) and a long open time (1200 seconds). After storing Part A for 4 weeks at 40°C, adhesion tests revealed that curing at 80°C had similar results to fresh adhesive (8.4 MPa vs. 8.5 MPa). There was a minor decline in 7-day curing (9.1 MPa vs.

[0108] 11.6 MPa) and a significant drop in fast curing (0.7 MPa vs. 3.2 MPa). The reduced performance suggests a kinetically slow interaction between Polycat SA4 and Mor-Free 88-138, which can be mitigated by thermal triggers. These results indicate limited aging stability of the system for standard operational conditions in EV battery applications (fast curing or room temperature curing).

[0109] IE1, IE2 show overall improvement for substrate adhesion for the cured and aged systems, polymeric catalyst complex that improves adhesion properties of the formulated 2K polyurethane adhesives. The combination of polymeric acidic polyol and tertiary amine in the proper ratio can lead to a highly stable catalyst, with a long reaction profile even at 45 °C and remarkable positive influence on the adhesion properties.

[0110] IE1 incorporates the latent catalyst derived from using the phosphate ester polyol as a blocking agent and the tertiary amine (DBU) as the catalytic blocked agent, in a 10 / 0.5 ratio. This example contains the same amount of active catalytic agent (0.3%) as CE2 and CE3, but demonstrates improved adhesion properties (5.6 MPa of LSS for full curing, 7.9 MPa for room temperature curing) compared to CE2 and CE3. Moreover, the catalyst complex shows an extended activation profile at 45°C, reaching 2000 Pa of shear stress at 1500 seconds, whereas CE2 and CE3 have gel times below 1000 seconds. This new polymeric catalyst not only exhibits latent properties but also enhances the adhesion of the formulated adhesive.

[0111] IE2 illustrates the impact of the ratio between the phosphate ester polyol and the tertiary amine on both gel time and adhesion. With a ratio of 10 / 0.1, significantly improved adhesion on aluminum is achieved (9.3 MPa of LSS for full curing, 12.7 MPa for room temperature curing). This latent catalyst also boosts adhesion during fast curing (5.8 MPa of LSS in 8 minutes). The ratio similarly affects gel time, as the shear stress does not reach 2000 Pa within the tested timeframe (>1500 seconds).

[0112] 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 two-component adhesive composition, comprising:A) an isocyanate-reactive component comprisingone or more vegetable oil polyols having a hydroxyl number according to ASTM D4274-21 in a range of 50 mg KOH / g to 400 mg KOH / g, a catalyst complex formed by one or more phosphate ester polyols and one or more tertiary amine catalysts, wherein the ratio of phosphate ester polyol to tertiary amine catalyst ranges from 100:1 to 10:1; andB) an isocyanate component comprising one or more isocyanate-terminated prepolymers.

2. The composition of claim 1, wherein the one or more phosphate ester polyol is prepared from a reaction of hydroxyl-terminated compounds, phosphoric acid or polyphosphoric acid, and a polyisocyanate.

3. The composition of claim 1, wherein the isocyanate-reactive component contains the one or more phosphate ester polyols at a percent by weight ranging from 2 wt% to 25 wt%.

4. The composition of claim 1, wherein the vegetable oil polyol is a castor oil or a castor oil- modified polyol.

5. The composition of claim 1, wherein the ratio of phosphate ester polyol to tertiary amine catalyst ranges from 100:1 to 20:1.

6. The composition of claim 1, wherein the one or more isocyanate-terminated prepolymer is based on dimer acid polyester polyol and a polyisocyanate.

7. The composition of claim 1, wherein the volume ratio of isocyanate-reactive component to the isocyanate component is in a range of 2: 1 to 5: 1.

8. The composition of claim 1, wherein the isocyanate component further comprises one or more rheology modifiers.

9. The composition of claim 1, wherein the isocyanate component further comprises a fumed silica.

10. The composition of claim 1, wherein the two-component adhesive composition produces an adhesive having a lap shear strength according to ASTM D1002 at seven days of 8 MPa or more.

11. The composition of claim 1, wherein the two-component adhesive composition produces an adhesive having a shear stress open time to surpass 2000 Pa at 45 °C according to ASTM D1002 of at least 1500 seconds.

12. A method of preparing a polyurethane adhesive composition, comprising:forming a curable mixture by combining an isocyanate-reactive component and an isocyanate component, the isocyanate-reactive component comprising:one or more vegetable oil polyols having a hydroxyl number according to ASTM D4274-21 in a range of 50 mg KOH / g to 400 mg KOH / g, a catalyst complex formed by one or more phosphate ester polyols and one or more tertiary amine catalysts, wherein the ratio of phosphate ester polyol to tertiary amine catalyst ranges from 100:1 to 10:1; andthe isocyanate component comprising one or more isocyanate-terminated prepolymers; applying the curable mixture to a first substrate;contacting the first substrate with a second substrate; andallowing the curable mixture to cure and form an adhesion between the first and second substrates.

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