Two-component polyurethane adhesive

Abstract

Provided herein is a two-part polyurethane adhesive.

Description

[Technical field]

[0001] The present invention relates to the field of adhesives, in particular two-part polyurethane adhesives. [Background technology]

[0002] The automotive industry has seen a trend towards lighter weight vehicles over the past decade. This trend has been driven mainly by regulations to reduce vehicle CO2 emissions. In recent years, lightweight construction strategies have been further accelerated by the increasing number of electric vehicles. The combination of the growing automotive market and the growing market share of electric vehicles has led to a large growth in the number of electric vehicles. To obtain long driving ranges, batteries with high energy density are required. Several battery strategies are currently based on concepts with different details, but common to all long-range battery concepts is the need for thermal management to deal with the heat generated during operation. Thermal interface materials are required to thermally connect the battery cells or modules to the cooling unit.

[0003] Battery cells generate heat during charging and discharging operations. To optimize efficiency and / or to avoid dangerous thermal runaway reactions, the cells need to be kept at a suitable operating temperature (preferably 25-40°C). For these reasons, some form of active cooling is generally used. An efficient method is to pump a cooled water / glycol mixture through channels that cool the metal base plate on which the battery cells / modules are placed. To avoid having an insulating air film between the cells and the cooling plate, a thermal interface material is employed.

[0004] A common method of assembling large batteries is to place battery cells into modules, which are then placed into a battery pack. A thermal interface material (TIM) is placed between the module and a cooling plate. The modules are typically secured with screws or other mechanical methods, as the TIM typically does not provide much structural support. To increase the operating range of the battery, an increase in energy density is desired. One way to increase energy density is to eliminate the module level and bond the cells directly onto the cooling plate. This is called "cell-to-pack" (CTP). Since single cells cannot be manually fixed in place, this arrangement requires a TIM to provide structural support to bond the cells to the cooling plate. This type of TIM is called a structural TIM or a thermally conductive adhesive.

[0005] Thermally conductive adhesives are also used to bond cells to modules and to bond heat exchangers to cooling plates or other components.

[0006] The key requirement for a thermally conductive adhesive is a thermal conductivity of at least 1.5 W / mK. In addition, a lap shear strength of more than 2 MPa is required. The cooling plate, and often the cells too, are made of aluminum. Therefore, good adhesion to aluminum is necessary.

[0007] Although polyurethane-based two-part (2K) thermally conductive adhesives are suitable for thermally conductive adhesive applications in terms of mechanical properties, elongation at break, and cure speed, some challenges remain. In particular, adhesion to untreated aluminum substrates is poor. To achieve high thermal conductivity, a large amount of thermally conductive filler is required. Aluminum hydroxide exhibits several advantages for the formulation of thermally conductive adhesives, due to its low density, excellent thermal conductivity, and low cost. The problem with the presence of high levels of aluminum hydroxide in polyurethane adhesives is that shelf life is impaired due to undesirable reactions of NCO groups with surface water or other hydroxyl groups of the filler. Summary of the Invention [Means for solving the problem]

[0008] In a first aspect, the present invention provides a method for producing a composition comprising the steps of: (A) (a1) 7.5 to 25% by weight, based on the total weight of solution A, of a blocked polyurethane prepolymer which is a reaction product of a polyisocyanate and a phenol; (a2) 3.5 to 15% by weight of at least one aromatic epoxy resin based on the total weight of Solution A; (a3) at least one epoxy silane; A first liquid comprising: (B) (b1) 8 to 18% by weight, based on the total weight of the solution B, of a nucleophilic crosslinking agent capable of reacting with the blocked polyurethane prepolymer (a1) and the aromatic epoxy resin (a2); (b2) a catalyst capable of promoting the reaction of the nucleophile (b1) with the blocked polyurethane prepolymer (a1) and the aromatic epoxy resin (a2); A second liquid containing; A two-part thermally conductive adhesive formulation comprising: the (A) liquid and / or the (B) liquid further contain a thermally conductive filler, the (A) liquid and the (B) liquid are designed to be blended together before use to form an adhesive, and the concentration of the thermally conductive filler in the adhesive is 60 to 80 wt % based on the total weight of the adhesive; A two-part thermally conductive adhesive formulation is provided.

[0009] In a second aspect, the present invention provides a method for producing a pharmaceutical composition comprising the steps of: (A) (a1) 9 to 25% by weight, based on the total weight of solution A, of a blocked polyurethane prepolymer which is a reaction product of a polyisocyanate and a phenol; (a2) 3.5 to 15% by weight of at least one aromatic epoxy resin based on the total weight of Solution A; (a3) at least one epoxy silane; A first liquid comprising: (B) (b1) 8 to 18% by weight, based on the total weight of the solution B, of a nucleophilic crosslinking agent capable of reacting with the blocked polyurethane prepolymer (a1) and the aromatic epoxy resin (a2); (b2) a catalyst capable of promoting the reaction of the nucleophile (b1) with the blocked polyurethane prepolymer (a1) and the aromatic epoxy resin (a2); A second liquid containing; A kit for a two-part thermally conductive adhesive formulation comprising: the (A) liquid and / or the (B) liquid further contain a thermally conductive filler, the (A) liquid and the (B) liquid are designed to be blended together before use to form an adhesive, and the concentration of the thermally conductive filler in the adhesive is 60 to 80 wt % based on the total weight of the adhesive; Provide a kit.

[0010] In a third aspect, the present invention provides a method of bonding a battery cell to a substrate, comprising the steps of: (1) (A) (a1) 9 to 25% by weight, based on the total weight of solution A, of a blocked polyurethane prepolymer which is a reaction product of a polyisocyanate and a phenol; (a2) 3.5 to 15% by weight of at least one aromatic epoxy resin based on the total weight of Solution A; (a3) at least one epoxy silane; A first liquid comprising: (B) (b1) 8 to 18% by weight, based on the total weight of the solution B, of a nucleophilic crosslinking agent capable of reacting with the blocked polyurethane prepolymer (a1) and the aromatic epoxy resin (a2); (b2) a catalyst capable of promoting the reaction of the nucleophile (b1) with the blocked polyurethane prepolymer (a1) and the aromatic epoxy resin (a2); A second liquid containing; preparing a two-part thermally conductive adhesive formulation comprising the steps of: (2) a step of mixing the (A) liquid with the (B) liquid to obtain an uncured adhesive, the concentration of the thermally conductive filler in the adhesive being 60 to 80% by weight based on the total weight of the adhesive; (3) applying the uncured adhesive to a battery cell, a substrate, or both; (4) bringing the battery cell into adhesive contact with the substrate; and (5) curing the adhesive; The present invention provides a method comprising:

[0011] In a fourth aspect, the present invention provides a method for producing a pharmaceutical composition comprising the steps of: (A) (a1) 9 to 25% by weight, based on the total weight of solution A, of a blocked polyurethane prepolymer which is a reaction product of a polyisocyanate and a phenol; (a2) 3.5 to 15% by weight of at least one aromatic epoxy resin based on the total weight of Solution A; (a3) at least one epoxy silane; A first liquid comprising: (B) (b1) 8 to 18% by weight, based on the total weight of the solution B, of a nucleophilic crosslinking agent capable of reacting with the blocked polyurethane prepolymer (a1) and the aromatic epoxy resin (a2); (b2) a catalyst capable of promoting the reaction of the nucleophile (b1) with the blocked polyurethane prepolymer (a1) and the aromatic epoxy resin (a2); A second liquid containing; 1. A bonded assembly including a battery cell bonded to a substrate by an adhesive formed by mixing the (A) liquid and / or the (B) liquid further contain a thermally conductive filler, the (A) liquid and the (B) liquid are designed to be blended together before use to form an adhesive, and the concentration of the thermally conductive filler in the adhesive is 60 to 80 wt % based on the total weight of the adhesive; A bonded assembly is provided. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The inventors have formulated a thermally conductive adhesive using a combination of blocked polyurethane resin, epoxy resin and silane, which provides i) high thermal conductivity, ii) It has been found that lap shear strengths of greater than 2 MPa, iii) excellent adhesion to aluminum substrates, and iv) excellent shelf life (storage stability) can be achieved.

[0013] Definitions and Abbreviations DSC Differential Scanning Calorimetry MDI 4,4'-methylenebis(phenylisocyanate) HDI Hexamethylene Diisocyanate IPDI Isophorone Diisocyanate PU Polyurethane SEC Size Exclusion Chromatography RH Relative humidity.

[0014] The equivalent weight and molecular weight were measured by gel permeation chromatography (GPC) using a Malvern Viscothek GPC max instrument. Tetrahydrofuran (THF) was used as the eluent, PL GEL MIXED D (Agilent, 300*7.5mm, 5μm) was used as the column, and MALVERN Viscotek TDA (integrated refractive index viscometer and light scattering) was used as the detector.

[0015] The adhesive of the present invention is a two-part polyurethane adhesive comprising parts A and B. Parts A and B can be packaged together as a kit. Parts A and B are mixed together in the appropriate ratio, preferably a 1:1 volume ratio, prior to use, and then applied to a substrate as soon as possible. Liquids A and B will be disclosed in more detail below.

[0016] A liquid Liquid A is (a1) 9 to 25% by weight, based on the total weight of solution A, of a blocked polyurethane prepolymer which is a reaction product of a polyisocyanate and a phenol; (a2) 3.5 to 15% by weight, based on the total weight of Solution A, of at least one aromatic epoxy resin; and (a3) at least one epoxy silane; Includes.

[0017] Blocked polyurethane prepolymer (a1) Liquid (A) of the adhesive composition is a phenol-capped reaction product of a polyisocyanate and a polyol, and preferably contains 9 to 25% by weight, more preferably 10 to 25% by weight, of a blocked polyurethane prepolymer which is a reaction product of 70 to 85% by weight of an aromatic polyisocyanate and 15 to 25% by weight of phenol, based on the total weight of Liquid A. Preferably, the reaction is carried out using a tin catalyst.

[0018] The polyisocyanate may be aliphatic, aromatic, or mixed, with aromatic polyisocyanates being preferred. Examples of aromatic polyisocyanates include methylene diphenyl diisocyanate (MDI), toluene diisocyanate (TDI), p-phenylene diisocyanate (PPDI), and naphthalene diisocyanate (NDI), all of which can be reacted with polyols. Particularly preferred are methylene diphenyl diisocyanate (MDI) or toluene diisocyanate (TDI) reacted with polyols.

[0019] The polyol is preferably a polyether polyol. The polyol may have two or more OH groups. Examples of polyether polyols include poly(alkylene oxide) diols, in which the alkylene groups are C2 to C6, particularly preferably the alkylene groups are C2 to C4. Examples of suitable polyols include poly(ethylene oxide) diol, poly(propylene oxide) diol, poly(tetramethylene oxide) diol. Poly(propylene oxide) diols, especially poly(propylene glycol), are particularly preferred.

[0020] Particularly preferred are the reaction products of aromatic diisocyanates with polyether polyols, especially those listed above, which are then capped with a phenol.

[0021] The phenol used for capping is preferably a phenol of the formula:

[0022] [ka]

[0023] (Wherein, R is a saturated or unsaturated C 15 R is preferably a saturated C 15 (It is a chain).

[0024] Particularly preferred are polyisocyanates prepared by reacting TDI with poly(propylene oxide) diols, especially when the resulting polyisocyanates have an equivalent weight of about 950.

[0025] Phenol-containing compounds typically have a straight chain hydrocarbon attached to the phenol group to provide some aliphatic character to the compound. The straight chain hydrocarbon preferably contains about 3 or more carbon atoms, more preferably about 5 or more carbon atoms, even more preferably about 8 or more carbon atoms, and most preferably about 10 or more carbon atoms. The straight chain hydrocarbon preferably contains about 50 or less carbon atoms, about 30 or less carbon atoms, about 24 or less carbon atoms, or about 18 or less carbon atoms. A particularly preferred phenol is cardanol.

[0026] In a preferred embodiment, the blocked polyurethane prepolymer is prepared by reacting methylene diphenyl diisocyanate (MDI) with a polyether polyol, particularly a poly(propylene oxide) diol.

[0027] In a preferred embodiment, the blocked polyurethane prepolymer is prepared by reacting methylene toluene diisocyanate (TDI) with a polyether polyol, particularly a poly(propylene oxide) diol.

[0028] In a particularly preferred embodiment, the blocked polyurethane prepolymer is made by reacting toluene diisocyanate with a polyether polyol having an NCO content of about 4-5% and an equivalent weight of about 500-1500 g / eq.

[0029] In another preferred embodiment, the blocked polyurethane prepolymer is prepared by reacting an aromatic polyisocyanate based on toluene diisocyanate with cardanol, preferably a polyisocyanate based on 70-85 wt.% TDI with 15-25 wt.% cardanol. Preferably, the reaction is carried out using a tin catalyst.

[0030] The molecular weight data of the polyurethane prepolymers were determined by gel permeation chromatography (GPC) using a Malvern Viscothek GPC max instrument, EMSURE-THF (ACS, Reag.Ph EUR, analytical grade) was used as the eluent, PL GEL MIXED D (Ailent, 300×7.5 mm, 5 μm) was used as the column, and MALVERN Viscotek TDA was used as the detector.

[0031] The blocked polyurethane prepolymer is present in an amount of 9 to 25% by weight, more preferably 10 to 25% by weight, 12 to 18% by weight, and particularly preferably 13 to 15% by weight, based on the total weight of Solution A.

[0032] Aromatic epoxy resin (a2) Part A contains 3.5-15 wt. %, preferably 5-15 wt. %, of an aromatic epoxy resin based on the total weight of part A. The aromatic epoxy resin is any epoxy resin based on bisphenol and epichlorohydrin. Examples of suitable bisphenols include bisphenol A, bisphenol AP, bisphenol AF, bisphenol B, bisphenol C, bisphenol E, bisphenol F, and bisphenol M. In a preferred embodiment, the bisphenol is bisphenol A.

[0033] The (A) liquid contains an aromatic epoxy resin. The aromatic epoxy resin is preferably a reaction product of a diphenol and epichlorohydrin. Examples of suitable diphenols include bisphenol A and bisphenol F, with bisphenol A being particularly preferred.

[0034] In a particularly preferred embodiment, the aromatic epoxy resin is the reaction product of epichlorohydrin and bisphenol A and has the following characteristics:

[0035] [Table 1]

[0036] In a preferred embodiment, the aromatic epoxy resin is a reaction product of epichlorohydrin and bisphenol A, has the following characteristics, and is present in an amount of 6 to 10% by weight based on the total weight of liquid (A):

[0037] [Table 2]

[0038] The aromatic epoxy resin preferably has a viscosity according to ASTM D-445 at 25° C. of 12,000 mPa.s or less, more preferably 11,000 mPa.s or less, and particularly preferably 10,000 mPa.s or less.

[0039] The aromatic epoxy resin preferably has an epoxide equivalent weight according to ASTM D-1652 of 150 to 250, more preferably 170 to 190 [not sure if this is important].

[0040] In a particularly preferred embodiment, the aromatic epoxy resin is based on bisphenol A and has an epoxide equivalent weight (per ASTM D-1652) of 176 to 185 and a viscosity per ASTM D-445 of 7,000 to 10,000 mPa.s at 25° C. A suitable such epoxy is sold under the trade name DER330.

[0041] The aromatic epoxy resin is present in Liquid A in an amount of 3.5 to 15% by weight, preferably 5 to 15% by weight, and more preferably 6 to 10% by weight, based on the total weight of Liquid A.

[0042] In a particularly preferred embodiment, the aromatic epoxy resin is based on bisphenol A, has an epoxide equivalent weight (per ASTM D-1652) of 176 to 185, and is present at 6 to 10 weight percent, based on the total weight of Part A.

[0043] In use, parts (A) and (B) are mixed prior to or simultaneously with application to a substrate. The concentration of aromatic epoxy resin in the final mixed adhesive can be calculated from the ratio of parts (A) and (B) used to make the final mixed adhesive. In a preferred embodiment, parts (A) and (B) are mixed in a 1:1 volume ratio, in which case the concentration of aromatic epoxy resin in the final adhesive will be half that of part (A).

[0044] Epoxy silane (a3) Part A contains an epoxysilane, which is a molecule with the following general formula:

[0045] [ka]

[0046] (In the formula, R 1 , R2 , and R 3 are independently selected from C1 to C3 alkyl; R 4 is a divalent organic radical).

[0047] In a preferred embodiment, R 1 , R 2 , and R 3 is independently selected from ethyl and methyl, with methyl being preferred, and in particular R 1 , R 2 , and R 3 is methyl.

[0048] R 4 is preferably an alkylene, preferably a C2-C 12 It is preferably selected from alkylene, more preferably C2 to C6 alkylene, and particularly preferably propylene.

[0049] In a particularly preferred embodiment, R 1 , R 2 , and R 3 is methyl and the wavy bond is an n-propylene radical [(γ-glycidoxypropyl)trimethoxysilane].

[0050] The epoxy silane is preferably present in Liquid A in an amount of 0.1 to 2% by weight, more preferably 0.25 to 1.5% by weight, and particularly preferably 0.3 to 0.6% by weight, based on the total weight of Liquid A.

[0051] In a particularly preferred embodiment, the epoxy silane is γ-glycidoxypropyltrimethoxysilane in an amount of 0.2 to 0.75% by weight, more preferably 0.25 to 0.6% by weight, and particularly preferably 0.5% by weight, based on the total weight of Liquid (A).

[0052] Thermally conductive filler The thermally conductive filler is not particularly limited.

[0053] Suitable thermally conductive fillers are those having a thermal conductivity coefficient of greater than 5 W / m°K, greater than 10 W / m°K, or greater than 15 W / m°K. Examples of thermally conductive fillers include alumina, alumina trihydrate or aluminum trihydroxide, silicon carbide, boron nitride, diamond, and graphite, or mixtures thereof. Particularly preferred embodiments are aluminum trihydroxide (ATH) and aluminum oxide, with ATH being most preferred.

[0054] In a preferred embodiment, the thermally conductive filler has a broad particle size distribution characterized by a D90 / D50 ratio of about 3 or greater. Particularly preferred, the thermally conductive filler is ATH or aluminum oxide, most preferably ATH, having a broad particle size distribution characterized by a D90 / D50 ratio of about 3 or greater.

[0055] Similarly, thermally conductive fillers having a bimodal particle size distribution are also preferred. 90 / D 50 The ratio is about 3 or more, more preferably about 5 or more, and even more preferably about 9 or more. For example, D of 5 to 20 microns 50 and D of 70 to 90 microns 90 , especially D of 7 to 9 microns 50 and D of 78 to 82 microns 90 The particle size can be determined using laser diffraction. For ATH, a suitable solvent is deionized water with a dispersing aid such as Na4P2O7x10H2O, preferably at 1 g / l. Preferred are aluminum oxide and ATH, especially ATH, with a bimodal distribution.

[0056] The thermally conductive filler is preferably present in the final adhesive at a concentration that provides a thermal conductivity of about 1.5 W / mK or greater. For example, this typically requires a concentration of thermally conductive filler of more than 50% by weight, more preferably more than 60% by weight, and more particularly preferably more than 70% by weight, based on the total weight of the adhesive. In a particularly preferred embodiment, the thermally conductive filler is present at more than 80% by weight, based on the total weight of the adhesive. Preferably, the content of thermally conductive filler in the final adhesive is less than 93% by weight, since higher levels may have a detrimental effect on adhesive strength and impact resistance. In a particularly preferred embodiment, the thermally conductive filler is present at 85-90% by weight, based on the total weight of the adhesive.

[0057] The thermally conductive filler may be present in the (A) liquid, the (B) liquid, or both. In a preferred embodiment, the thermally conductive filler is present in both the (A) and (B) liquids because its presence in both reduces the amount of mixing required to properly distribute the thermally conductive filler when the (A) and (B) liquids are mixed. Preferably, it is present in similar or equal concentrations in both the (A) and (B) liquids. In a particularly preferred embodiment, it is present in the final mixture of the (A) and (B) liquids at 85-90% by weight, based on the total weight of the mixture. Preferably, it is present in both the (A) and (B) liquids at 85% by weight, based on the weight of the relevant liquid.

[0058] In a particularly preferred embodiment, the thermally conductive filler is D 90 / D 50 The ATH has a ratio of about 8 or more and is used in both solutions (A) and (B) at a concentration of 85 to 89% by weight based on the total weight of solution (A) or solution (B).

[0059] B liquid: Liquid B is (b1) 8 to 18% by weight, preferably 11 to 18% by weight, of a nucleophilic crosslinking agent capable of reacting with the blocked polyurethane prepolymer (a1) and the aromatic epoxy resin (a2), based on the total weight of the solution B; (b2) a catalyst capable of promoting the reaction of the nucleophile (b1) with the blocked polyurethane prepolymer (a1) and the aromatic epoxy resin (a2); Includes.

[0060] Nucleophilic crosslinker (b1) The liquid B contains 8 to 18% by weight, preferably 11 to 18% by weight, of a nucleophilic crosslinking agent based on the total weight of the liquid B.

[0061] The nucleophilic crosslinker is preferably a diamine or triamine, with triamines being preferred. The amine groups may independently be secondary or primary, with primary being preferred.

[0062] The nucleophilic crosslinking agent preferably has a molecular weight of 1,500 to 4,000 Da, more preferably 2,000 to 3,500 Da, with approximately 3,000 Da being particularly preferred.

[0063] The nucleophilic crosslinking agent is preferably a poly(alkylene oxide) diol, in particular having a backbone based on C2-C6 alkylenes, more particularly C2-C4 alkylenes, with C3 alkylenes being most preferred. Particularly preferably, the backbone is based on a polyether of propylene glycol. Preferably, it is a diamine or triamine with the aforementioned backbone.

[0064] In a particularly preferred embodiment, the nucleophilic crosslinker is a triamine having greater than 90% of the amine groups being primary amines, a molecular weight of about 3,000 Da, and a backbone based on a polyether of propylene glycol.

[0065] More particularly preferably, the nucleophilic crosslinker is a trifunctional polyetheramine of molecular weight about 3000:

[0066] [ka]

[0067] and has the following characteristics:

[0068] [Table 3]

[0069] The nucleophilic crosslinking agent is present in Liquid (B) at a concentration of 8 to 18% by weight, 11 to 18% by weight, and more preferably 12 to 14% by weight, based on the total weight of Liquid (B).

[0070] In a particularly preferred embodiment, the nucleophilic crosslinker is a trifunctional polyetheramine of about 3000 molecular weight:

[0071] [ka]

[0072] and has the following characteristics, and is 11 to 14% by weight based on the total weight of liquid (B).

[0073] [Table 4]

[0074] In use, parts (A) and (B) are mixed prior to or simultaneously with application to a substrate. The concentration of the nucleophilic crosslinker in the final mixed adhesive can be calculated from the ratio of parts (A) and (B) used to make the final mixed adhesive. In a preferred embodiment, parts (A) and (B) are mixed in a 1:1 volume ratio, in which case the concentration of the nucleophilic crosslinker in the final adhesive will be half that of part (A).

[0075] Catalyst (b2) The (B) liquid contains a catalyst capable of promoting the reaction of the nucleophile (b1) with the blocked polyurethane prepolymer (a1) and the aromatic epoxy resin (a2).

[0076] The catalyst is preferably selected from Lewis bases and Lewis acids, with preference given to diazabicyclo[2.2.2]octane, tris-2,4,6-((dimethylamino)methyl)phenol, DMDEE (2,2'-dimorpholinodiethyl ether), imidazoles such as 4-methylimidazole, triethanolamine, and tertiary amines including polyethyleneimine.

[0077] Organotin compounds such as dioctyltin dineodecanoate, and other metal catalysts such as tetrabutyl titanate, zirconium acetylacetonate, and bismuth neodecanoate are also suitable.

[0078] Particularly preferred is a combination of diazabicyclo[2.2.2]octane and tris-2,4,6-((dimethylamino)methyl)phenol.

[0079] The catalyst is used in an amount of preferably 0.05 to 0.6% by weight, more preferably 0.075 to 0.5% by weight, and most preferably about 0.5% by weight, based on the total weight of liquid (B).

[0080] In a preferred embodiment, the catalyst is a combination of 0.2 to 0.6 wt % tris-2,4,6-((dimethylamino)methyl)phenol and 0.05 to 0.2 wt % diazabicyclo[2.2.2]octane, and more particularly preferably a combination of 0.4 wt % tris-2,4,6-((dimethylamino)methyl)phenol and 0.1 wt % diazabicyclo[2.2.2]octane.

[0081] Optional Components of Part A and / or Part B Liquid (A) and liquid (B) are Esters of unsaturated fatty acids, especially C 16 ~C 18 Plasticizers such as esters of fatty acids, especially methyl esters, tris(2-ethylhexyl) phosphate, and phosphate esters, for example tris(2-ethylhexyl) phosphate; · Stabilizers such as polycaprolactone; · dyes and colorants; · Fillers such as carbon black, calcium carbonate, glass fibre, wollastonite etc. (other than thermally conductive fillers); · Viscosity reducers such as hexadecyltrimethoxysilane; It may further include other ingredients such as:

[0082] Cured thermally conductive adhesive The present invention also provides a cured thermally conductive adhesive obtained by mixing and curing liquid (A) and liquid (B).

[0083] Parts (A) and (B) can be mixed in any ratio. Preferably, the final concentrations of the components, after mixing (A) and (B), fall within the following ranges, based on the total weight of the adhesive:

[0084] [Table 5]

[0085] Application to substrate Parts (A) and (B) can be mixed and applied to a substrate using known methods such as a manual application system or an automated method using a pump system using a 20 liter pail or a 200 liter drum or any other suitable container.

[0086] Features The cured adhesive composition is characterized by a thermal conductivity of 1.5 W / mK or greater, as measured according to ASTM 5470-12 (described in the Examples).

[0087] The cured adhesive composition preferably has a lap shear strength of at least 1.8 MPa, more preferably more than 2.2 MPa, more particularly preferably more than 2.5 MPa after curing according to DIN EN1465:2009 and standing for 7 days at 23°C and 50% relative humidity as measured in the examples.

[0088] The cured adhesive composition has a failure mode of greater than 80% cohesive failure, more preferably greater than 90% cohesive failure, after curing and standing for 7 days at 23° C. and 50% relative humidity, as measured according to the Examples.

[0089] The adhesive also features excellent storage stability with less than 80% increase in viscosity of Part A after two weeks of storage at room temperature.

[0090] The two-part composition cures (preferably characterized by changing from a paste to a solid within 24 hours after mixing) at room temperature.

[0091] Battery assembly and method The present invention also provides a battery assembly including a battery module secured in place within the assembly by a cured adhesive composition obtained by mixing parts (A) and (B) so as to provide thermal conductivity between the cell and the substrate when the mixture is cured, and / or by mechanical fastening means.

[0092] The (A) and (B) solutions are mixed in a desired ratio, and the mixture is applied and cured in a manner that physically and electrically isolates the battery cells and secures them in place on a substrate designed to cool the cells, such that when the mixture hardens it provides thermal conductivity between the cells and the substrate.

[0093] The thermal conductivity of the adhesive in the assembly is preferably 1.5 W / mK or greater, as measured according to ASTM 5470-12 (as described in the examples).

[0094] Particularly preferred embodiments The following are particularly preferred embodiments of the present invention. 1. A kit for a two-part thermally conductive adhesive formulation comprising: (A) (a1) 9 to 25% by weight, based on the total weight of solution A, of a blocked polyurethane prepolymer which is a reaction product of a polyisocyanate and a phenol; (a2) 3.5 to 15% by weight of at least one aromatic epoxy resin based on the total weight of Solution A; (a3) at least one epoxy silane; A first liquid comprising: (B) (b1) 8 to 18% by weight, based on the total weight of the solution B, of a nucleophilic crosslinking agent capable of reacting with the blocked polyurethane prepolymer (a1) and the aromatic epoxy resin (a2); (b2) a catalyst capable of promoting the reaction of the nucleophile (b1) with the blocked polyurethane prepolymer (a1) and the aromatic epoxy resin (a2); A second liquid containing; A two-part thermally conductive adhesive formulation comprising: the (A) liquid and / or the (B) liquid further contain a thermally conductive filler, the (A) liquid and the (B) liquid are designed to be blended together before use to form an adhesive, and the concentration of the thermally conductive filler in the adhesive is 60 to 80 wt % based on the total weight of the adhesive; A two-part thermally conductive adhesive formulation.

[0095] 2. A kit for a two-part thermally conductive adhesive formulation comprising: (A) (a1) 9 to 25% by weight, based on the total weight of solution A, of a blocked polyurethane prepolymer which is a reaction product of a polyisocyanate and a phenol; (a2) 3.5 to 15% by weight of at least one aromatic epoxy resin based on the total weight of Solution A; (a3) at least one epoxy silane; A first liquid comprising: (B) (b1) 8 to 18% by weight, based on the total weight of the solution B, of a nucleophilic crosslinking agent capable of reacting with the blocked polyurethane prepolymer (a1) and the aromatic epoxy resin (a2); (b2) a catalyst capable of promoting the reaction of the nucleophile (b1) with the blocked polyurethane prepolymer (a1) and the aromatic epoxy resin (a2); A second liquid containing; A kit for a two-part thermally conductive adhesive formulation comprising: the (A) liquid and / or the (B) liquid further contain a thermally conductive filler, the (A) liquid and the (B) liquid are designed to be blended together before use to form an adhesive, and the concentration of the thermally conductive filler in the adhesive is 60 to 80 wt % based on the total weight of the adhesive; kit.

[0096] 3. A method of bonding a battery cell to a substrate, comprising: The process is as follows: (1) (A) (a1) 9 to 25% by weight, based on the total weight of solution A, of a blocked polyurethane prepolymer which is a reaction product of a polyisocyanate and a phenol; (a2) 3.5 to 15% by weight of at least one aromatic epoxy resin based on the total weight of Solution A; (a3) at least one epoxy silane; A first liquid comprising: (B) (b1) 8 to 18% by weight, based on the total weight of the solution B, of a nucleophilic crosslinking agent capable of reacting with the blocked polyurethane prepolymer (a1) and the aromatic epoxy resin (a2); (b2) a catalyst capable of promoting the reaction of the nucleophile (b1) with the blocked polyurethane prepolymer (a1) and the aromatic epoxy resin (a2); A second liquid containing; preparing a two-part thermally conductive adhesive formulation comprising the steps of: (2) a step of mixing the (A) liquid with the (B) liquid to obtain an uncured adhesive, the concentration of the thermally conductive filler in the adhesive being 60 to 80% by weight based on the total weight of the adhesive; (3) applying the uncured adhesive to a battery cell, a substrate, or both; (4) bringing the battery cell into adhesive contact with the substrate; and (5) curing the adhesive; The method includes:

[0097] 4. (A) (a1) 9 to 25% by weight, based on the total weight of solution A, of a blocked polyurethane prepolymer which is a reaction product of a polyisocyanate and a phenol; (a2) 3.5 to 15% by weight of at least one aromatic epoxy resin based on the total weight of Solution A; (a3) at least one epoxy silane; A first liquid comprising: (B) (b1) 8 to 18% by weight, based on the total weight of the solution B, of a nucleophilic crosslinking agent capable of reacting with the blocked polyurethane prepolymer (a1) and the aromatic epoxy resin (a2); (b2) a catalyst capable of promoting the reaction of the nucleophile (b1) with the blocked polyurethane prepolymer (a1) and the aromatic epoxy resin (a2); A second liquid containing; 1. A bonded assembly including a battery cell bonded to a substrate by an adhesive formed by mixing the (A) liquid and / or the (B) liquid further contain a thermally conductive filler, the (A) liquid and the (B) liquid are designed to be blended together before use to form an adhesive, and the concentration of the thermally conductive filler in the adhesive is 60 to 80 wt % based on the total weight of the adhesive; Bonded assembly.

[0098] 5. Any one of the preceding embodiments, wherein the blocked polyurethane prepolymer is a phenol-capped reaction product of a polyisocyanate and a polyol.

[0099] 6. Any one of the preceding embodiments, wherein the blocked polyurethane prepolymer comprises 70-85% by weight aromatic polyisocyanate (i.e., a diisocyanate reacted with a polyol) and 15-25% by weight phenol.

[0100] 7. Embodiment 5 or 6, wherein the polyisocyanate is aliphatic, aromatic, or a mixture.

[0101] 8. Embodiment 5 or 6, wherein the polyisocyanate is an aromatic polyisocyanate.

[0102] 9. Any one of the preceding embodiments, wherein the blocked polyurethane prepolymer is made using a polyisocyanate selected from methylene diphenyl diisocyanate (MDI), toluene diisocyanate (TDI), p-phenylene diisocyanate (PPDI), and naphthalene diisocyanate (NDI).

[0103] 10. Any one of the preceding embodiments, wherein the blocked polyurethane prepolymer is made using methylene diphenyl diisocyanate (MDI) or toluene diisocyanate (TDI).

[0104] 11. Any one of the preceding embodiments, wherein the blocked polyurethane prepolymer is made using a polyether polyol.

[0105] 12. Any one of the preceding embodiments, wherein the blocked polyurethane prepolymer is made using a poly(alkylene oxide) diol in which the alkylene group is C2-C6, and particularly preferably in which the alkylene group is C2-C4.

[0106] 13. Any one of the preceding embodiments, wherein the blocked polyurethane prepolymer is made using a poly(propylene oxide) diol, particularly poly(propylene glycol).

[0107] 14. Any one of the preceding embodiments wherein the blocked polyurethane prepolymer is made by reacting an aromatic diisocyanate with a polyether polyol, particularly those listed above, followed by capping with a phenol.

[0108] 15. Any one of the preceding embodiments, wherein the blocked polyurethane prepolymer is capped with a phenol of the following formula:

[0109] [ka]

[0110] (Wherein, R is a saturated or unsaturated C 15 R is preferably a saturated C 15 (It is a chain).

[0111] 16. Any one of the preceding embodiments, wherein the blocked polyurethane prepolymer is capped with cardanol.

[0112] 17. Any one of the preceding embodiments wherein the blocked polyurethane prepolymer is produced by reacting TDI with poly(propylene oxide) diol, particularly when the resulting polyisocyanate has an equivalent weight of about 950.

[0113] 18. Any one of the preceding embodiments, wherein the blocked polyurethane prepolymer is made by reacting methylene diphenyl diisocyanate (MDI) with a polyether polyol, in particular a poly(propylene oxide) diol.

[0114] 19. Any one of the preceding embodiments, wherein the blocked polyurethane prepolymer is made by reacting toluene diisocyanate with a polyether polyol and has an NCO content of about 4-5% and an equivalent weight of about 500-1500 g / eq.

[0115] 20. Any one of the preceding embodiments, wherein the blocked polyurethane prepolymer is produced by reacting an aromatic polyisocyanate based on toluene diisocyanate with cardanol, preferably by reacting 70-85 wt.% TDI-based polyisocyanate with 15-25 wt.% cardanol.

[0116] 21. Any one of the preceding embodiments, wherein the blocked polyurethane prepolymer is present at 12-18 wt%, more preferably 13-15 wt%, based on the total weight of Part A.

[0117] 22. Any one of the preceding embodiments, wherein the aromatic epoxy resin is an epoxy resin based on bisphenol and epichlorohydrin.

[0118] 23. Any one of the preceding embodiments, wherein the aromatic epoxy resin is an epoxy resin based on bisphenol A, bisphenol AP, bisphenol AF, bisphenol B, bisphenol C, bisphenol E, bisphenol F, bisphenol M.

[0119] 24. Any one of the preceding embodiments, wherein the aromatic epoxy resin is a bisphenol A-based epoxy resin.

[0120] 25. Any one of the preceding embodiments, wherein the aromatic epoxy resin is a reaction product of epichlorohydrin and bisphenol A, and has the following characteristics:

[0121] [Table 6]

[0122] 26. Any one of the preceding embodiments, wherein the aromatic epoxy resin is used in an amount of 3.5 to 15 wt %, more preferably 6 to 10 wt %, based on the total weight of Part A.

[0123] 27. An epoxy silane having the following general formula:

[0124] [ka]

[0125] (In the formula, R 1 , R 2 , and R 3are independently selected from C1 to C3 alkyl; R 4 is a divalent organic radical. Any one of the preceding embodiments, wherein the molecule is

[0126] 28.R 1 , R 2 , and R 3 is independently selected from ethyl and methyl.

[0127] 29.R 1 , R 2 , and R 3 is methyl.

[0128] 30.R 4 is alkylene, preferably C2 to C 12

[0081] Embodiments 27, 28, or 29, wherein the alkylene is selected from alkylene, more preferably C2 to C6 alkylene, and particularly preferably propylene.

[0129] 31. Any one of the preceding embodiments, wherein the epoxy silane is (γ-glycidoxypropyl)trimethoxysilane.

[0130] 32. Any one of the preceding embodiments, wherein the epoxy silane is present in Part A at 0.1 to 2 wt. %, more preferably 0.25 to 1.5 wt. %, and particularly preferably 0.3 to 0.6 wt. %, based on the total weight of Part A.

[0131] 33. Any one of the preceding embodiments, wherein the epoxy silane is 0.2 to 0.75 wt. %, more preferably 0.25 to 0.6 wt. %, and particularly preferably about 0.5 wt. % γ-glycidoxypropyltrimethoxysilane, based on the total weight of the (A) liquid.

[0132] 34. Any one of the preceding embodiments, wherein the thermally conductive filler is selected from those having a thermal conductivity coefficient greater than 5 W / m°K, greater than 10 W / m°K, or greater than 15 W / m°K.

[0133] 35. Any one of the preceding embodiments, wherein the thermally conductive filler is selected from alumina, alumina trihydrate, aluminum trihydroxide, silicon carbide, boron nitride, diamond, and graphite, or mixtures thereof.

[0134] 36. Any one of the preceding embodiments, wherein the thermally conductive filler is aluminum trihydroxide (ATH).

[0135] 37. Any one of the preceding embodiments, wherein the thermally conductive filler is ATH having a broad particle size distribution characterized by a D90 / D50 ratio of about 3 or greater.

[0136] 38. Any one of the preceding embodiments, wherein the thermally conductive filler has a bimodal particle size distribution.

[0137] 39. The thermally conductive filler has a ratio D of 3 or more, more preferably 5 or more, and more particularly preferably 9 or more. 90 / D 50 Any one of the preceding embodiments, comprising:

[0138] 40. The thermally conductive filler has a ratio D of 3 or more, more preferably 5 or more, and more particularly preferably 9 or more. 90 / D 50 Any one of the preceding embodiments, wherein the ATH has the formula:

[0139] 41. Any one of the preceding embodiments, wherein the thermally conductive filler is present in the final adhesive at a concentration that provides a thermal conductivity of about 1.5 W / mK or greater.

[0140] 42. Any one of the preceding embodiments, wherein the thermally conductive filler is present in the final adhesive at greater than 50% by weight, more preferably greater than 60% by weight, and even more particularly preferably greater than 70% by weight.

[0141] 43. Any one of the preceding embodiments, wherein the thermally conductive filler is present in the final adhesive at greater than 80% by weight.

[0142] 44. Any one of the preceding embodiments, wherein the thermally conductive filler is present in the final adhesive at 85-90% by weight.

[0143] 45. Thermally conductive filler is D 90 / D 50 Any one of the preceding embodiments, wherein the ATH has a ratio of about 8 or greater and is used in both parts (A) and (B) at a concentration of 85-89% by weight, based on the total weight of part (A) or part (B).

[0144] 46. ​​Any one of the preceding embodiments, wherein the nucleophilic crosslinker is a diamine or triamine.

[0145] 47. Any one of the preceding embodiments, wherein the nucleophilic crosslinker is a triamine.

[0146] 48. Any one of the preceding embodiments, wherein the nucleophilic crosslinker is a diamine or triamine, and the amine groups are independently secondary or primary, with primary being preferred.

[0147] 49. Any one of the preceding embodiments, wherein the nucleophilic crosslinker has a molecular weight of 1,500-4,000 Da, more preferably 2,000-3,500 Da, with about 3,000 Da being particularly preferred.

[0148] 50. Any one of the preceding embodiments, wherein the nucleophilic crosslinker has a backbone based on a poly(alkylene oxide) diol, particularly a C2-C6 alkylene, more particularly a C2-C4 alkylene, with C3 alkylene being most preferred.

[0149] 51. Any one of the preceding embodiments, wherein the nucleophilic crosslinker is based on a polyether of propylene glycol.

[0150] 52. Any one of the preceding embodiments, wherein the nucleophilic crosslinker is a triamine having greater than 90% of the amine groups being primary amines, a molecular weight of about 3,000 Da, and a backbone based on a polyether of propylene glycol.

[0151] 53. The nucleophilic crosslinker is a trifunctional polyetheramine of approximately 3000 molecular weight:

[0152] [ka]

[0153] Any one of the preceding embodiments, wherein

[0154] [Table 7]

[0155] 54. Any one of the preceding embodiments, wherein the nucleophilic crosslinker is present in the (B) liquid at a concentration of 8-18% by weight, more preferably 12-14% by weight, based on the total weight of the (B) liquid.

[0156] 55. Any one of the preceding embodiments, wherein the catalyst is selected from a Lewis base and a Lewis acid.

[0157] 56. Any one of the preceding embodiments, wherein the catalyst is selected from diazabicyclo[2.2.2]octane, tris-2,4,6-((dimethylamino)methyl)phenol, DMDEE (2,2'-dimorpholinodiethyl ether), imidazoles such as 4-methylimidazole, triethanolamine, polyethyleneimine.

[0158] 57. Any one of the preceding embodiments, wherein the catalyst is diazabicyclo[2.2.2]octane in combination with tris-2,4,6-((dimethylamino)methyl)phenol.

[0159] 58. The catalyst is (B) Any one of the preceding embodiments, wherein the (B) is used at 0.05 to 0.6 wt. %, more preferably 0.075 to 0.5 wt. %, and even more preferably about 0.5 wt. %, based on the total weight of the liquid.

[0160] 59. Any one of the preceding embodiments, wherein the catalyst is a combination of 0.2-0.6 wt. % tris-2,4,6-((dimethylamino)methyl)phenol and 0.05-0.2 wt. % diazabicyclo[2.2.2]octane, more particularly preferably a combination of 0.4 wt. % tris-2,4,6-((dimethylamino)methyl)phenol and 0.1 wt. % diazabicyclo[2.2.2]octane.

[0161] 60. Any one of the previous embodiments, wherein the cured adhesive composition has a thermal conductivity, measured according to ASTM 5470-12 (as described in the Examples), of 1.5 W / mK or greater.

[0162] 61. The cured adhesive composition has a compressive strength of preferably 2.5 MPa or more, more preferably 1.0 MPa or more, after being left for 7 days at 23°C and 50% relative humidity after curing according to DIN EN1465:2009 as measured in the examples. Any one of the preceding embodiments, having a lap shear strength greater than 2.6 MPa.

[0163] 62. Any one of the preceding embodiments, wherein the cured adhesive composition has a failure mode of greater than 80% cohesive failure, more preferably greater than 90% cohesive failure, after curing and aging for 7 days at 23° C. and 50% relative humidity, as measured according to the examples.

[0164] 63. Any one of the preceding embodiments, wherein Part A exhibits less than 80% increase in viscosity after 3 months at room temperature.

[0165] 64. Any one of the preceding embodiments, wherein the two-part composition cures at room temperature (preferably characterized by a change from a paste to a solid after aging for 24 hours after mixing). EXAMPLES

[0166] [Table 8]

[0167] [Table 9]

[0168] method Press-in force: The press-in force was measured with a tensometer (Zwick). Uncured adhesive was placed on a metal surface. An aluminum piston of 40 mm diameter was placed on top and the material was compressed to 5 mm (initial position). The material was then compressed to 0.3 mm at a speed of 1 mm / s and the force-displacement curve was recorded. The force (N) at a thickness of 0.5 mm was then reported and considered as the press-in force.

[0169] Thermal conductivity: Thermal conductivity was measured on a ZFW Stuttgart Thermal Interface Materials Tester according to ASTM 5470-17. A and B components are mixed in a 1:1 volume ratio using a side-by-side cartridge and a pneumatic application gun. The materials are mixed in a helical static mixer with 24 mixing elements and a diameter of 10 mm. Plates with a thickness of 2 mm were prepared and cured for 7 days at 23°C and 50% relative humidity. Disks with a diameter of 30 mm were cut from the cured plates and used for the thermal conductivity tests. The thermal conductivity tests are performed in pressure mode applying pressures of 1, 2, 3, 5, and 10 bar. The top contact was heated to about 40°C and the bottom contact was heated to about 10°C, resulting in a sample temperature of about 25°C.

[0170] GPC: Molecular weight data of polyurethane prepolymers were measured by gel permeation chromatography (GPC) using a Malvern Viscotek GPC max instrument. EMSURE-THF (ACS, Reag.Ph EUR, analytical grade) was used as eluent, PL GEL MIXED D (Ailent, 300×7.5 mm, 5 μm) was used as column, and MALVERN Viscotek TDA was used as detector.

[0171] Formulation preparation: Formulations were mixed in a planetary mixer or a dual asymmetric centrifuge. In the first stage, the liquid phase was mixed and then the solid ingredients were added to the formulation. The formulations were mixed under vacuum for approximately 30 minutes before being filled into cartridges, pails, or drums.

[0172] Lap shear test: Aluminum substrates (AA6061 T6 1.92mm MF noPT no lub, 140×25mm, 1.9mm thickness, from Novelis) were used. The substrates were cleaned with isopropanol before use. After the thermal interface material was applied to one substrate, the second substrate was bonded within 5 minutes. The thickness was adjusted to 1.0mm, and the overlap area was 25mm×25mm. The material was cured and left at 23°C and 50% relative humidity for 7 days before lap shear testing. The lap shear specimens were then mounted on a tensile meter and lap shear testing was performed using a pulling speed of 10mm / min. The force deflection curves were observed. The strength at break was reported as lap shear strength.

[0173] Viscosity: Rheological measurements were performed on an Anton Paar MC302 rheometer in parallel plate geometry. Plates of 25 mm diameter were used with a fixed gap of 0.5 mm. The thermal interface material was placed between the two plates and shear rate tests were performed from 0.001 to 20 l / s. Viscosity at 10 l / s was reported.

[0174] Formulations were prepared using the ingredients listed in Table 2.

[0175] [Table 10]

[0176] [Table 11]

Claims

1. 1. A two-part thermally conductive adhesive formulation comprising: (A) (a1) 9 to 25% by weight, based on the total weight of Solution A, of a blocked polyurethane prepolymer which is a reaction product of a polyisocyanate and a phenol; (a2) 3.5 to 15 wt % of at least one aromatic epoxy resin based on the total weight of Part A; (a3) at least one epoxy silane; a first liquid comprising: (B) (b1) 8 to 18% by weight, based on the total weight of Solution B, of a nucleophilic crosslinking agent capable of reacting with the blocked polyurethane prepolymer (a1) and the aromatic epoxy resin (a2); (b2) a catalyst capable of promoting the reaction of a nucleophile (b1) with the blocked polyurethane prepolymer (a1) and the aromatic epoxy resin (a2); a second liquid comprising: Including, the (A) liquid and / or the (B) liquid further contain a thermally conductive filler, the (A) liquid and the (B) liquid are designed to be blended together to form an adhesive before use, and the concentration of the thermally conductive filler in the adhesive formulation is 60 to 80 wt % based on the total weight of the adhesive formulation; Two-part thermally conductive adhesive formulation.

2. 10. The adhesive formulation of claim 1, wherein the blocked polyurethane prepolymer is a phenol-capped reaction product of a polyisocyanate and a polyol.

3. 10. The adhesive formulation of claim 1, wherein the blocked polyurethane prepolymer comprises 70 to 85 weight percent aromatic polyisocyanate and 15 to 25 weight percent phenol, based on the total weight of the prepolymer.

4. 4. The adhesive formulation of claim 3, wherein the polyisocyanate is aliphatic, aromatic, or a mixture thereof.

5. The adhesive formulation of claim 3 wherein the polyisocyanate is an aromatic polyisocyanate.

6. 10. The adhesive formulation of claim 1, wherein the blocked polyurethane prepolymer is made using a polyisocyanate selected from methylene diphenyl diisocyanate (MDI), toluene diisocyanate (TDI), p-phenylene diisocyanate (PPDI), and naphthalene diisocyanate (NDI).

7. 10. The adhesive formulation of claim 1, wherein the blocked polyurethane prepolymer is made using methylene diphenyl diisocyanate (MDI) or toluene diisocyanate (TDI).

8. 10. The adhesive formulation of claim 1, wherein the blocked polyurethane prepolymer is made using a polyether polyol.

9. The blocked polyurethane prepolymer has an alkylene group of C 2 ~C 6 10. The adhesive formulation of claim 1 made using a poly(alkylene oxide) diol wherein

10. 10. The adhesive formulation of claim 1, wherein the blocked polyurethane prepolymer is made using a poly(propylene oxide) diol.

11. 10. The adhesive formulation of claim 1, wherein the blocked polyurethane prepolymer is prepared by reacting an aromatic diisocyanate with a polyether polyol followed by capping with a phenol.

12. 10. The adhesive formulation of claim 1, wherein the blocked polyurethane prepolymer is capped with a phenol of the following formula: 【Chemical 1】 (Wherein R is a saturated or unsaturated C 15 chain).

13. 10. The adhesive formulation of claim 1, wherein the blocked polyurethane prepolymer is capped with cardanol.

14. 10. The adhesive formulation of claim 1, wherein the blocked polyurethane prepolymer is made by reacting TDI with poly(propylene oxide) diol, the resulting polyisocyanate having an equivalent weight of about 950.

15. 10. The adhesive formulation of claim 1, wherein the blocked polyurethane prepolymer is made by reacting methylene diphenyl diisocyanate (MDI) with a polyether polyol.

16. 10. The adhesive formulation of claim 1, wherein the blocked polyurethane prepolymer is made by reacting toluene diisocyanate with a polyether polyol and has an NCO content of about 4-5% and an equivalent weight of about 500-1500 g / eq.

17. 10. The adhesive formulation of claim 1, wherein the blocked polyurethane prepolymer is made by reacting an aromatic polyisocyanate based on toluene diisocyanate with cardanol.

18. 10. The adhesive formulation of claim 1, wherein the blocked polyurethane prepolymer is present at 12 to 18 weight percent based on the total weight of Part A.

19. 10. The adhesive formulation of claim 1, wherein the aromatic epoxy resin is an epoxy resin based on bisphenol and epichlorohydrin.

20. 2. The adhesive formulation of claim 1, wherein the aromatic epoxy resin is an epoxy resin based on bisphenol A, bisphenol AP, bisphenol AF, bisphenol B, bisphenol C, bisphenol E, bisphenol F, or bisphenol M.

21. 10. The adhesive formulation of claim 1, wherein the aromatic epoxy resin is a bisphenol A-based epoxy resin.

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