UNDER AMBIENT CONDITIONS

CLAIM OF PRIORITY

[001] The present application claims priority to US Provisional Patent Application 62/532, 101 filed on July 13, 2017, the contents of which is incorporated herein by reference in its entirety. FIELD

[002] Disclosed are latent two-part polyurethane adhesives that rapidly develop adhesive strength when cured under ambient conditions. Further disclosed are methods of bonding structures together using the latent two-part polyurethane adhesives.

BACKGROUND

[003] Polyurethanes are a well-known type of adhesive. They contain precursor materials that cure in place to form an adhesive layer. Polyurethane adhesives come in one-part and two-part types. One-part types generally exhibit a moisture cure or a heat-activated cure. Two- part types consist of a resin component that includes one or more polyisocyanate compounds, and a curative component that includes one or more compounds having two or more isocyanate reactive compounds, for example polyols. When the two components are mixed, the polyisocyanates and one or more compounds having two or more isocyanate reactive compounds, for example polyols, react to form a cured polyurethane adhesive. A polyurethane adhesive can be formulated to cure at room temperature or upon exposure to certain conditions, an example of which is an elevated temperature. As the adhesive cures, it can form a strong adhesive bond to many types of substrates.

[004] Two part curable compositions are used in a variety of applications such as adhesives, coatings, foams and the like. Two part compositions are used where rapid cure is required for the application, especially where the two parts are not shelf stable when in contact with one another. Shelf stable means that the composition does not cure in storage. It is desirable that the adhesive composition exhibit a suitable open time and cure rapidly. The "open time" refers to the amount of time after the two components are mixed that the adhesive remains flowable and capable of bonding to a substrate. One way of obtaining both a long open time and a fast cure is by formulating the adhesive to have a heat-activated cure. Such an adhesive cures slowly at ambient temperature, thereby allowing the adhesive to be applied and the substrates positioned while the adhesive remains flowable. The resulting assembly is then heated to an elevated temperature at which rapid curing takes place.

[005] Two part fast curing two part adhesives are disclosed in WO2014/040909 and US2015/0203728, incorporated herein by reference, in its entirety, for all purposes. Such two part adhesive systems provide limited flexibility. Process flexibility may be defined as long open time that is the time between application of the adhesive to a first substrate and joining of a second substrate to the first substrate using the adhesive. Further long mixer stand-alone times, the time the mixed two part adhesive can be kept in the mixer unit (static or dynamic) between two applications without gelling, are required to reduce the flushing intervals and therefore reduce waste. Fast cure, as evidenced by fast strength build up, once the open time window closes is desired to provide handling strength as soon as possible after final assembly of the components.

[006] Two part curable adhesive systems having excellent latency have been developed that are curable by the application of heat, such as by infrared heating systems. Examples of these systems are disclosed in WO2016/205251 ; WO2016205252; WO2016205254; and WO2016205255; all incorporated herein by reference, in their entirety, for all purposes. These systems exhibit excellent latency and control over bonding substrates together where heating systems are used to intiate cure. These systems require the use of heating systems for initiating cure and thus include the capital costs for such systems. Some substrates cannot withstand exposure to the heating used for curing. Some process for bonding substrates do not justify the cost of installing heating systems. Thus there is a need for two part adhesive systems that can cure under ambient conditions and provide reasonable latency.

[007] Thus, what is needed is a two part adhesive that provides long open times, sufficient cure strength after one hour to allow handling of bonded parts under ambient conditions. What are needed are bonding methods using two part adhesives that allow reasonable time to contact and locate substrates to one another with the adhesive disposed between the substrates which cure under ambient conditions, wherein the substrates can be handled after about one hour.

SUMMARY

[008] Disclosed are compositions comprising two parts: wherein Part 1 , the polyisocyanate part, comprises; a) one or more polyisocyanates: and Part 2, the isocyanate reactive or polyol part, comprises; b1) one or more compounds containing isocyanate reactive groups: and b2) one or more blocked compounds including a blocked amine group. The blocked compound preferably is an association complex. The blocked amine group is blocked by a boron containing compound including. The amine group preferably is blocked by an association between the boron atom of the boron containing compound and a nitrogen atom of the amine group. The amine group preferably is a tertiary amine or a secondary ketimine. The blocked amine group dissociates upon contact with the one or more polyisocyanates and the unblocked amine groups catalyze the reaction of isocyanates with isocyanate reactive groups. The borane containing compound that blocks the amine group preferably corresponds to the formula: B(H) _a (X) (R) _c :wherein B represents Boron; H represents Hydrogen; X is independently in each occurrence a halogen, alkoxy, carboxylate or acetate group; R independently in each occurrence a lower alkyl group; a is independently in each occurrence a integer of from 1 to 3; b is independently in each occurrence a integer of from 0 to 2; and c is independently in each occurrence a integer of from 0 to 1 ; wherein either or both of b or c are 0. The tertiary amine or the secondary ketimine may be an aromatic or cycloaliphatic structure with pending tertiary amines or aromatic or cycloaliphatic structures with one or more nitrogen atoms incorporated into the ring structures. The blocked compounds including the blocked amine group preferably is present in Part 2 in an amount of about 0.01 to about 8 percent by weight, more preferably 0.05 to about 5 percent by weight. The composition may contain one or more latent room temperature organometallic catalysts. The one or more latent room temperature organometallic catalysts may be located in Part 2. The isocyanate reactive compounds may comprise one or more low molecular weight isocyanate reactive compounds containing two or more isocyanate reactive groups and one or more polyalkylene oxides containing two or more isocyanate reactive groups. Preferably, the composition includes one or more polyalkylene oxides containing two or more isocyanate reactive groups present in an amount of about 35 to about 80 percent by weight of Part 2; one or more low molecular weight isocyanate reactive compounds present in an amount of about 1 to about 10 percent by weight of Part 2; and, one or more polyisocyanates present in an amount of about 20 to about 65 percent by weight of Part 1. The polyisocyanates may comprise one or more isocyanate functional prepolymers.

[009] Disclosed is a method comprising: a) contacting the Part 1 (e.g., the polyisocyanate part), and Part 2 (e.g., the isocyanate reactive part, or the polyol part), and mixing to form a mixture, which is preferably a substantially homogeneous or entirely homogeneous mixture; and b) applying the mixture to a first substrate. The method preferably comprises: c) contacting a second substrate with the first substrate with the mixture of part a disposed between the first and second substrate. The mixture of Part 1 and Part 2 may cure without application of heat. The mixture of Part 1 and Part 2 may cure under ambient conditions. The mixture of Part 1 and Part 2 may cure and bond two or more substrates together. The first substrate and second substrate may be bonded together upon cure of the mixture of step a. The mixture of Part 1 and Part 2 may cure when exposed to a temperature of about 15 °C to about 50 °C. Dissimilar substrates may be bonded together by curing the mixture of step a while contacting and being interposed between the dissimilar substrate. One or both of the first substrate and the second substrate may comprise metal, fiber reinforced polymers, coated metal, polymers or coated polymers.

[0010] Disclosed is a composition comprising one or more blocked compounds including a blocked amine group blocked by a boron containing compound. The blocked compound includes one or more tertiary amines and/or one or more secondary ketimines which are blocked by an association between the nitrogen atom of the amine group and the boron atom of the boron containing compound. Preferably, all of the tertiary amines and secondary ketimines capable of forming an association with a boron containing compound (e.g., with a borane) are blocked. It will be appreciated that the amine containing compound may additionally include one or more amines that are incapable for forming an association with the boron containing compound due to steric hindrance or other constraints, such as in a nitrogen atom that is part of two ring structures. The blocked compound may include an aromatic or a cycloaliphatic structure, having one or more rings. The nitrogen atom of the blocked amine group may be pendant from the aromatic or cycloaliphatic structure, or the nitrogen atom may be incorporated into one or more rings. The aromatic or a cycloaliphatic structure may contain one or more heteroatoms other than nitrogen, for example oxygen or oxygen containing functional groups. Each blocked amine group may be blocked with boron containing compounds that are the same or that are different. By way of example, each boron containing compound may be a borane. The blocked compound may include one or more tertiary amine which are each disposed on alkyl groups bound to an aromatic ring. The blocked compound may contain more than one blocked amine groups. For example, the blocked compound may contain more than one blocked tertiary amines, or more than one blocked secondary ketimines. The blocked compound may contain a cyclic amidine structure. The blocked compound (which preferably is an association complex) may correspond to one of the formulas:

wherein B represents Boron; H represents Hydrogen; X is independently in each occurrence a halogen, alkoxy, carboxylate or acetate group; R is independently in each occurrence a lower alkyl group; R ² is independently in each occurrence one or more cyclic aliphatic or aromatic rings, which may contain one or more hydrocarbyl groups bonded to the one or more rings and one or more heteroatoms in the cyclic rings or the hydrocarblyl groups, arranged such that the nitrogen atom is tertiary, has three bonds to it; R ³ is independently in each occurrence a hydrocarbyl group which may contain one or more heteroatoms; R ⁴ is independently in each occurrence a lower alkyl group; a is independently in each occurrence an integer of from 1 to 3; b is independently in each occurrence a integer of from 0 to 2; c is independently in each occurrence a integer of from 0 to 1 ; wherein either or both of b or c are 0; d is independently in each occurrence an integer of 0 to 2; and e is independently in each occurrence an integer of from 1 to 3.

[0011] The adhesive composition adheres strongly to many substrates. The adhesives bond well to fiber reinforced plastic substrates. The adhesives exhibit lap shear strengths 1 hour after application of about 0.3 MPa or greater, about 0.5 MPa or greater or about 0.8 MPa or greater. The adhesives exhibit lap shear strengths 24 hours after application of about 6 MPa or greater, about 7 MPa or greater, or about 8 MPa or greater. The adhesive composition exhibits good latency, as exhibited by long open time and high 1 hour lap shear strength (such as an open time of about 4 minutes or greater, about 5 minutes or greater, about 6 minutes or greater or about 8 minutes or greater, and a one-hour lap shear strength of about 0.3 MPa or greater, about 0.5 MPa or greater or about 0.8 MPa or greater. This is a significant advantage, as it permits the adhesive composition to be formulated for an ambient temperature cure if desired. Despite its latency, the adhesive cures well at room temperature, without the need for applied heating (apart from an exothermic temperature rise due to the curing reaction itself). The adhesive compositions exhibit relatively long open times and rapid strength build up after the open time window closes. The adhesives exhibit an open time of about 4 minutes or greater, about 5 minutes or greater, about 6 minutes or greater or about 8 minutes or greater. The adhesives exhibit an open time of about 30 minutes or less.

DETAI LED DESCRIPTION

[0012] The explanations and illustrations presented herein are intended to acquaint others skilled in the art with the invention, its principles, and its practical application. The specific embodiments of the present invention as set forth are not intended as being exhaustive or limiting of the invention. The scope of the invention should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. The disclosures of all articles and references, including patent applications and publications, are incorporated by reference for all purposes. Other combinations are also possible as will be gleaned from the following claims, which are also hereby incorporated by reference into this written description.

[0013] Disclosed is a curable composition comprising two parts: wherein Part 1 , the polyisocyanate part, comprises; a) one or more polyisocyanates: and Part 2, the isocyanate reactive or polyol part, comprises; b1) one or more compounds containing isocyanate reactive groups: and b2) one or more blocked compounds including a blocked amine group which is blocked by a boron containing compound. The blocked amine group includes an amine group that is a tertiary amine or a secondary ketimine. The boron-containing compound includes a boron atom that associates with the nitrogen of the amine group to form an association complex. Preferably, all of the tertiary amines and secondary ketimines capable of forming an association with the boron containing compound are blocked. The blocked amine groups dissociate upon contact with the one or more polyisocyanates and the unblocked amine groups (e.g. tertiary amine or secondary ketimine) catalyze the reaction of isocyanates with isocyanate reactive groups. The compositions exhibit rapid cure with good latency under ambient conditions. Ambient cure refers to cure under conditions existing in a plant. Ambient temperatures may include a temperature of about 15 °C to about 50 °C during cure or about 20 °C to about 35 °C

[0014] One or more as used herein means that at least one, or more than one, of the recited components may be used as disclosed. Nominal as used with respect to functionality means the theoretical functionality, generally this can be calculated from the stoichiometry of the ingredients used. The actual functionality may be different due to imperfections in raw materials, incomplete conversion of the reactants and formation of by-products. Durability in this context means that the composition once cured remains sufficiently strong to perform its designed function, for instance the adhesive holds substrates together for the life or most of the life of the structure containing the cured composition. As an indicator of this durability, the curable composition (e.g. adhesive) preferably exhibits excellent results during accelerated aging. This may mean that after a set of substrates bonded with the adhesive is exposed to heat aging, the failure mode in Quick Knife adhesion or Lap Shear testing is cohesive, meaning the adhesive breaks before the bond of the adhesive to the substrate breaks. Isocyanate content means the weight percent of isocyanate groups in the designated component, such as a prepolymer. The isocyanate content can be measured by analytical techniques known to one skilled in the art, for example by potentiometric titration with an active hydrogen containing compound, such as dibutyl amine. The residual content of a component can be calculated from the ingredients utilized to prepare the component or composition. Alternatively, it can be determined utilizing known analytical techniques. Heteroatom means nitrogen, oxygen, sulfur and phosphorus, or nitrogen and oxygen. Hydrocarbyl refers to a group containing one or more carbon atom backbones and hydrogen atoms, which may optionally contain one or more heteroatoms. Where the hydrocarbyl group contains heteroatoms, the heteroatoms may form one or more functional groups well known to one skilled in the art. Hydrocarbyl groups may contain cycloaliphatic, aliphatic, aromatic or any combination of such segments. The aliphatic segments can be straight or branched. The aliphatic and cycloaliphatic segments may include one or more double and/or triple bonds. Included in hydrocarbyl groups are alkyl, alkenyl, alkynyl, aryl, cycloalkyi, cycloalkenyl, alkaryl and aralkyi groups. Cycloaliphatic groups may contain both cyclic portions and noncyclic portions. Hydrocarbylene means a hydrocarbyl group or any of the described subsets having more than one valence, such as alkylene, alkenylene, alkynylene, arylene, cycloalkylene, cycloalkenylene, alkarylene and aralkylene. As used herein percent by weight or parts by weight refer to, or are based on, the weight or the curable compositions unless otherwise specified. Based on the weight of or total weight the composition means the weight of both the polyol and the isocyanate component unless stated otherwise. Parts by weight refer to 100 parts by weight.

[0015] The term isocyanate-reactive compound as used herein includes any organic compound having nominally at least two isocyanate-reactive moieties. An isocyanate reactive moiety can be an active hydrogen containing moiety which refers to a moiety containing a hydrogen atom which, because of its position in the molecule, displays significant activity according to the

Zerewitinoff test described by Wohler in the Journal of the American Chemical Society, Vol. 49, p. 3181 (1927). Illustrative of such isocyanate reactive moieites, such as active hydrogen moieties, are — COOH, —OH, — NH ₂ , — NH— , — CONH ₂ , — SH, and — CONH— . Active hydrogen containing compounds, isocyanate reactive moiety containing compounds, include polyols, polyamines, polymercaptans, and polyacids. The isocyanate reactive compound may be a polyol, or may be a polyether polyol. The at least two isocyanate-reactive moieties (e.g., the active hydrogen moieties) may be the same or different.

[0016] Part 1 of the composition contains one or more polyisocyanates. The polyisocyanates that may be utilized include any polyisocyanates that react with compounds containing isocyanate reactive groups to undergo curing, which impart significant cohesive strength to the cured composition and which enhance bonding to substrates. The polyisocyanates can be monomeric, oligomeric or prepolymers prepared from polyisocyanates reacted with compounds containing isocyanate reactive groups to prepare prepolymers having isocyanate groups. The polyisocyanates may be a mixture of isocyanate functional prepolymers and unreacted compounds having more than one, two or more, isocyanate groups. Such mixture may be formed as a result of reacting an equivalents excess of polyisocyanates with compounds containing more than one isocyanate reactive groups.

[0017] The prepolymer may be a reaction product of one or more polyisocyanates and one or more isocyanate reactive compounds. The prepolymer may be a reaction product of one or more aromatic diisocyanates having a molecular weight of up to 350 with i) at least one 700 to 3000 molecular weight homopolymer of poly(propylene oxide) having a nominal hydroxyl functionality of 2 to 4, or ii) a mixture of i) with up to 3 parts by weight, per part by weight of i), of a 2000 to 8000 molecular weight polyether polyol which is a copolymer of 70 to 99 weight percent propylene oxide and 1 to 30 weight percent ethylene oxide and has a nominal hydroxyl functionality of 2 to 4. The poly(propylene oxide) used to make the prepolymer may have a molecular weight of 800 to 2000 or from 800 to 1500, and has and may have a nominal functionality of 2 to 3. A copolymer of 70 to 99 weight percent propylene oxide and 1 to 30 weight percent ethylene oxide used to make the pre-olymer may have a molecular weight of 3000 to 5500 and a nominal functionality of 2 to 3.

[0018] The reaction of polyisocyanate and polyol(s), as the compounds containing isocyanate reactive groups, produces prepolymer molecules having a polyether segment that is capped with the polyisocyanate, so the molecules have terminal isocyanate groups. Each prepolymer molecule contains a polyether segment that corresponds to the structure, after removal of hydroxyl groups, of a polyol used in the prepolymer-forming reaction. If a mixture of polyols is used to make the prepolymer, a mixture of prepolymer molecules is formed.

[0019] The isocyanate-terminated prepolymer may have an isocyanate equivalent weight of about 700 to about 3500, about 700 to about 3000 or about 1000 to about 3000. The equivalent weight may be calculated by adding the weight of the polyol(s) used to prepare the prepolymer and the weight of polyisocyanate(s) consumed in reaction with the polyol(s), and dividing by the number of moles of isocyanate groups in the resulting prepolymer. The polyisocyanate used to make the prepolymer may be any of the low equivalent weight polyisocyanate compounds mentioned below, or a mixture of two or more of these. The prepolymer may have 2 or greater, 2 to 4, or 2 to 3, isocyanate groups per molecule. The isocyanate groups of the prepolymer may be aromatic, aliphatic (including alicyclic), or a mixture of aromatic and aliphatic isocyanate groups. The isocyanate groups on the prepolymer molecules may be aromatic. The low equivalent weight polyisocyanate compound(s) in some embodiments may have an isocyanate equivalent weight of 80 to 250, 80 to 200, or 80 to 180. If a mixture of polyisocyanate compounds is present, the mixture may have, for example, an average of 2 to 4 or 2.3 to 3.5 isocyanate groups per molecule.

[0020] All or a portion of the low equivalent weight polyisocyanate compound may have aromatic isocyanate groups. Exemplary aromatic polyisocyanate compounds m-phenylene diisocyanate, toluene-2,4-diisocyanate, toluene-2,6-di-isocyanate, naphtha-ylene-1 ,5- diisocyanate, methoxyphenyl-2,4-diiso-cyanate, diphenyl-methane-4,4'-diisocyanate, diphenylmethane-2,4'-diisocyanate, 4,4'-bi-phenylene diisocyanate, 3,3'-dimeth-oxy-4,4'- biphenyl diisocyanate, 3,3'-dimethyl-4-4'-biphenyl diisocyanate, 3,3'-dimethyl-diphenyl methane-4,4'-diisocyan-ate, 4,4',4"-triphenyl methane triisocyanate, polymethylene polyphenylisocyanate (PMDI), toluene-2,4,6-triisocyanate and 4,4'-dimethyl-diphenylmethane- 2,2',5,5'-tetraiso-cyanate. Modified aromatic polyisocyanates that contain urethane, urea, biuret, carbodiimide, uretoneimine, allophonate or other groups formed by reaction of isocyanate groups are also useful. The aromatic polyisocyanate may be MDI or PMDI (or a mixture thereof that is commonly referred to as "polymeric MDI"), and so-called "liquid MDI" products that are mixtures of MDI and MDI derivatives that have biuret, carbodiimide, uretoneimine and/or allophonate linkages. All or a portion of the low equivalent weight polyisocyanate compounds may be one or more aliphatic polyisocyanates. Examples of these include cyclohexane diisocyanate, 1 ,3- and/or 1 ,4-bis(isocyanatomethyl)cyclohexane, 1-methyl- cyclohexane-2,4-diisocyanate, 1-methyl-cyclohexane-2,6-diisocyanate, methylene dicyclohexane diisocyanate, isophorone diisocyanate and hexamethylene diisocyanate.

[0021] At least some of the polyisocyanate groups present in the polyisocyanate component may be aromatic isocyanate groups. If a mixture of aromatic and aliphatic isocyanate groups may be present, about 50% or more by number or about 75% or more by number, are aromatic isocyanate groups. 80 to 98% by number of the isocyanate groups may be aromatic, and 2 to 20% by number may be aliphatic. All of the isocyanate groups of the prepolymer may be aromatic, and the isocyanate groups of the polyisocyanate compound(s) having an isocyanate equivalent weight of up to 350 may be a mixture of 80 to 95% aromatic isocyanate groups and 5 to 20% aliphatic isocyanate groups.

[0022] The isocyanate functional prepolymers are the reaction product of one or more polyisocyanates and one or more isocyanate reactive compounds wherein an excess of polyisocyanate may be present on an equivalents basis. The isocyanate reactive compounds may comprise one or more polyols. Exemplary polyols include those disclosed in Wu, U.S. Pat.

No. 6,512,033 at column 4, line 10 to line 64, incorporated herein by reference, for example, polyether polyols, polyester polyols, poly(alkylene carbonate) polyols, hydroxyl containing polythioethers and mixtures thereof. The polyols may be polyether polyols containing one or more alkylene oxide units in the backbone of the polyol. The isocyanate reactive compounds may be a mixture of one or more polyether diols and/or one or more polyether triols. Exemplary alkylene oxide units include ethylene oxide, propylene oxide, butylene oxide and mixtures thereof. The alkylene oxides may contain straight or branched chain alkylene units. The polyol may contain propylene oxide units, ethylene oxide units or mixtures thereof. Mixtures of alkylene oxide may be arranged randomly or in blocks. The polyol may comprise propylene oxide chains with ethylene oxide chains capping the polyol. The ethylene oxide capped polypropylene oxides may be hydrophobic, and may contain about 20 mole percent or less of ethylene oxide or about 10 mole percent or less of ethylene oxide in the backbone. The isocyanate-reactive compound may have a functionality of about 1.8 or greater, about 1.9 or greater, or about 1.95 or greater. The isocyanate-reactive compound may have a functionality of about 4.0 or less, about 3.5 or less, or about 3.0 or less. The equivalent weight of the isocyanate-reactive compound may be about 200 or greater, about 500 or greater or about

1 ,000 or greater. The equivalent weight of the isocyanate-reactive compound may be about

5,000 or less, about 3,000 or less, or about 2,500 or less. The compositions may further comprise one or more prepolymers containing one or more polyether polyols having dispersed therein or grafted to the backbone one or more organic based polymer particles. Exemplary organic based polymer particles may be based on thermoplastic polymers such as monovinylidene aromatic based polymers and copolymers of monovinylidene aromatic monomers with conjugated dienes, acrylates, methacrylates, unsaturated nitriles or mixtures thereof. The copolymers can be block or random copolymers. The particles may comprise copolymers of unsaturated nitrites, conjugated dienes and a monovinylidene aromatic monomer, a copolymer of an unsaturated nitrile and a monovinylidene aromatic monomer or a polyurea. The particles may comprise a polyurea or polystyrene-acrylonitrile copolymer. The particles may comprise polystyrene-acrylonitrile copolymers. The organic polymer particles are commonly available and well-known to those skilled in the art. The organic polymer particles may have a particle size which is large enough to improve the impact properties and elastomeric properties of the finally cured adhesive, but not so large so as to reduce the ultimate strength of the adhesive after cure. The particle size may be about 10 microns or greater or about the particle size is about 20 microns or greater. The particle size may be about

50 microns or less or about 40 microns or less. The polyols may contain about 20 percent by weight or greater of organic polymer particles, about 30 percent by weight or greater or about

35 percent by weight or greater. The polyols may contain about 60 percent by weight or less of organic polymer particles, about 50 percent by weight or less or about 45 percent by weight or less. The exemplary polyols containing organic polymer particles are disclosed in Zhou, U.S.

Pat. No. 6,709,539 at column 4, line 13 to column 6, line 18, incorporated herein by reference. The polyols containing the organic particles may comprise one or more polyether triols. The prepolymers containing organic based polymer particles may be present is sufficient amount to enhance the elastomeric nature and the modulus of the compositions. Such prepolymers may be present in the composition in an amount of about 5 percent by weight or less. Such prepolymers may be present in the composition in an amount of greater than 0 if present or about 0.1 percent by weight or greater.

[0023] The isocyanate reactive compounds may be present in an amount sufficient to react with most of the isocyanate groups of the isocyanates leaving enough isocyanate groups to correspond with the desired isocyanate content of the prepolymer.

[0024] The compounds containing isocyanate reactive groups may be present in an amount of about 50 percent by weight or greater based on the prepolymer, about 65 percent by weight or greater or about 80 percent by weight or greater. The compounds containing isocyanate reactive groups may be present in an amount of about 90 percent by weight or less based on the prepolymer or about 85 percent by weight or less.

[0025] A prepolymer may be prepared by combining one or more compounds containing two or more isocyanate reactive functional groups, such as polyols or polyol mixtures, with an amount of low equivalent weight polyisocyanate compound(s) significantly greater than needed to simply cap the isocyanate reactive functional groups, for example polyol(s). After reaction, this produces a mixture of the prepolymer and unreacted low equivalent weight polyisocyanate compounds. If desired, an additional amount of polyisocyanate compound(s) can then be blended into this mixture. The one or more compounds containing two or more isocyanate reactive functional groups, polyol(s), may be combined and reacted with an excess of one or more aromatic polyisocyanates to produce a mixture of prepolymer and unreacted starting polyisocyanate compounds, and this mixture then is combined with one or more aliphatic polyisocyanates. The prepolymer may be made in a reaction of the polyol(s) with MDI, PMDI, a polymeric MDI, a derivative of any one or more of these that contains biuret, carbodiimide, uretoneimine and/or allophonate, or a mixture of any two or more of these, to produce a mixture of prepolymer and unreacted starting polyisocyanates, and the mixture may then combined with one or more aliphatic polyisocyanates, especially an aliphatic polyisocyanate based on hexamethylene diisocyanate.

[0026] Part 1 , the polyisocyanate component, may contain up to 50% by weight of one or more particulate inorganic fillers as described before. Part 1 , the polyisocyanate component, may contain about 10% by weight or more, about 20% by weight or more of one or more such fillers, and may contain, for example, 20 to 50% or 30 to 40% by weight thereof. The filler amounts are based on the weight of Part 1 , the polyisocyanate component. The filler may exclude carbon particles.

[0027] Part 1 , the polyisocyanate component, may also contain one or more other additional ingredients, such as those described above with respect to the Part 2. Part 1 , the polyisocyanate component, may contain about 0.5% by weight or less, about 0.1 % by weight or less of organic compounds having a boiling temperature of 80°C or less, about 0.1 % by weight or less, or about 0.05% by weight or less, of water and/or other chemical blowing agents that produce a gas under the conditions of the curing reaction. Part 1 , the polyisocyanate component, may contain about 0 to 50 percent by weight of plasticizers as described with respect to Part 2. Part 1 , the isocyanate component, may be devoid of a plasticizer.

[0028] The viscosity of the isocyanate functional prepolymers may be about 200 Pa.s or less, about 150 Pa.s or less or about 120 Pa.s or less. The viscosity of the isocyanate functional prepolymers may be about 50 Pa.s or greater. The viscosity of the compositions can be adjusted with fillers. Below about 50 Pa.s a composition prepared from the isocyanate functional polymers may exhibit poor high speed tensile strength. Above about 150 Pa.s the isocyanate functional components, prepolymer, may be unstable and hard to pump. "Viscosity" as used herein is measured by the Brookfield Viscometer, Model DV-E with a RV spindle #5 at a speed of 5 revolutions per second and at a temperature of 23° C.

[0029] Part 1 , polyisocyanate component, may contain one or more polyisocyanate compounds. The polyisocyanate may be a mixture of one or more isocyanate-terminated prepolymers having at least 2 isocyanate groups per molecule and an isocyanate equivalent weight of 700 to 3500, and one or more low equivalent weight polyisocyanate compounds that have an isocyanate equivalent weight of up to 350 and 2 to 4 isocyanate groups per molecule.

When such a mixture is present, the prepolymer may constitute 20 to 65 percent of the weight of the polyisocyanate component. The prepolymer may constitutes 20 to 60 percent, 20 to 50 percent or 25 to 35 percent of the weight of the polyisocyanate component. The low equivalent weight polyisocyanate, when such a mixture is present, may constitute 20 to 50 weight percent of weight of the polyisocyanate component. The isocyanate content of the prepolymers may be about 1 percent by weight or greater, about 6 percent by weight or greater, about 8 percent by weight or greater or about 10 percent by weight or greater. The isocyanate content in the isocyanate functional prepolymers may be about 35 percent by weight or less, about 30 percent by weight or less, about 25 percent by weight or less or about 15 percent by weight or less.

[0030] Part 2 comprises one or more compounds containing isocyanate reactive groups. Any one or more compounds containing isocyanate reactive groups which provide the desired final properties may be utilized in the composition. The one or more compounds containing isocyanate reactive groups can be one or more chain extenders, crosslinking agents, polyols or polyamines. Polyols as described hereinbefore can be utilized as the one or more compounds containing isocyanate reactive groups. The polyols or polyamines can be prepolymers as described herein-before prepared utilizing excess equivalents of active hydrogen functional groups such that the resulting prepolymers contain active hydrogen functional groups, for example hydroxyl and or amino groups. The one or more compounds containing isocyanate reactive groups may comprise one or more low molecular weight compounds having two or more isocyanate reactive groups and a hydrocarbon backbone wherein the backbone may further comprise one or more heteroatoms. It is advantageous to use such low molecular weight compounds in two-part compositions. Such low molecular weight compounds may be compounds known in the art as chain extenders, difunctional compounds, or crosslinkers, having, on average, greater than two active hydrogen groups per compound. The molecular weight of the low molecular weight compound may be about 250 or less, about 120 or less or about 100 or less. The low molecular weight compound may comprise one or more multifunctional alcohols, multifunctional alkanol amines, one or more adducts of multifunctional alcohol and an alkylene oxide, one or more adducts of a multifunctional alkanol amine and an alkylene oxide or a mixture thereof. The low molecular weight compound may be used in a sufficient amount to obtain the desired G-Modulus (E-Modulus). In two-part compositions, the low molecular compound may be located Part 2. The low molecular weight compound may present in Part 2 in an amount of about 2 percent by weight or greater, about 3.0 percent by weight or greater or about 4.0 percent by weight or greater. The low molecular weight compound may be present in the composition in an amount of about 12 percent by weight or less, about 10 percent by weight or less or about 8 percent by weight or less.

[0031] Part 2 may further comprise polyoxyalkylene polyamine having 2 or greater amines per polyamine. The polyoxyalkylene polyamine may have 2 to 4 amines per polyamine or 2 to 3 amines per polyamine. The polyoxyalkylene polyamine may have a weight average molecular weight of about 200 or greater or about 400 or greater. The polyoxyalkylene polyamine may have a weight average molecular weight of about 5,000 or less or about 3,000 or less. Exemplary polyoxyalkylene polyamines are JEFFAMINE™ D-T-403 polypropylene oxide triamine having a molecular weight of about 400 and JEFFAMINE™ D-400 polypropylene oxide diamine having a molecular weight of about 400. The polyoxyalkylene polyamines may be present in a sufficient amount to prevent the composition from sagging once mixed and applied. The polyoxyalkylene polyamine may be present in Part 2 in an amount of about 0.2 percent by weight or greater, about 0.3 percent by weight or greater or about 0.5 percent by weight or greater. The polyoxyalkylene polyamine may be present in the Part 2 in an amount of about 6 percent by weight or less, about 5 percent by weight or less or about 4 percent by weight or less.

[0032] The one or more compounds containing isocyanate reactive groups may be one or more polyether polyols. Each such polyether polyol may have a hydroxyl equivalent weight of

400 to 2000. The hydroxyl equivalent weight of each polyol may be at least 500, at least 800 or at least 1000, and may be up to 1800, up to 1500 or up to 1200. Each such polyether polyol may have a nominal hydroxyl functionality of 2 to 4. By "nominal functionality" of a polyether polyol, or compounds containing isocyanate reactive groups, it is meant the average number of oxyalkylatable hydrogen atoms on the initiator compound that is alkoxylated to form the polyether polyol. The actual functionalities of the polyether polyol(s) may be somewhat lower than the nominal functionality, due to side-reactions that occur during the alkoxylation process. In the case of a mixture of polyether polyols, the number average nominal functionality may be 2 to 3.5 or 2.5 to 3.5. The polyether polyol(s) may be selected from homopolymers of propylene oxide and copolymers of 70 to 99% by weight propylene oxide and 1 to 30% by weight ethylene oxide. Such a copolymer of propylene oxide and ethylene oxide may be utilized if a single polyether polyol is present. If two or more polyether polyols are present, at least one is such may be a copolymer of propylene oxide and ethylene oxide. In the case of a copolymer, the propylene oxide and ethylene oxide may be randomly copolymerized, block copolymerized, or both. About 50% or more of the hydroxyl groups of the polyether polyol or mixture of polyether polyols may be primary hydroxyl, with the remainder being secondary hydroxyl groups. 70% or more of the hydroxyl groups in the polyether polyol or mixture thereof may be primary hydroxyl.

[0033] The polyether polyol(s) may constitute about 35 weight percent or greater of Part 2. The polyether polyol(s) may constitute about 40 weight percent or greater or about 50 weight percent or greater of Part, 2 may constitute about 80 weight percent or less, about 65 weight percent or less or about 55 weight percent or less.

[0034] Part 2 may comprise one or more aliphatic diol chain extenders. The aliphatic diol chain extender(s) may each have a hydroxyl equivalent weight of about 200 or less, about 100 or less, about 75 or less or about 60 or less, and about two aliphatic hydroxyl groups per molecule. Examples of these are monoethylene glycol, di-ethylene glycol, triethylene glycol, 1 ,2-propane diol, 1 ,3-propane diol, 2,3-dimethyl-1 ,3-propanediol, dipropylene glycol, tripropylene glycol, 1 ,4-butanediol, 1 ,6-hexanediol and other linear or branched alkylene diols having up to about 20 carbon atoms. The aliphatic diol chain extender may be monoethylene glycol, 1 ,4-butanediol or a mixture thereof. The chain extender may be present in an amount of about 0.1 percent by weight or greater of Part 2, about 1.0 percent by weight or greater, about 2.0 percent by weight or greater, about 3 percent by weight or greater or about 4 percent by weight or greater. The chain extender may be present in an amount of about 25 percent by weight or less of Part 2, about 10 percent by weight or less, about 9 percent by weight or less, about 8 percent by weight or less, about 7 percent by weight or less or about 6 percent by weight or less. The aliphatic diol chain extender or mixture thereof may be present in an amount of 2.5 to 6 equivalents per equivalent of the polyols of Part 2.

[0035] Part 2 of the composition contains one or more blocked compounds including one or more blocked amine groups. The blocked amine group is preferably a tertiary amine or a secondary ketimine which is blocked by a boron containing compound. The blocked compound may be an association complex including an association between an amine containing compound (i.e., including the tertiary amine and/or the secondary ketimine) and the boron containing compound. The blocked compound may be characterized by an association between the boron atom of the boron containing compound and a nitrogen atom of the amine group. Preferably each tertiary amine and each secondary ketimine capable of forming an association with a boron containing compound is blocked. Each blocked amine group may dissociate from the boron containing compound to free the amine groups to facilitate the desired cure properties. Any blocked compound wherein each tertiary amine (if present) and each secondary ketimine (if present) is blocked with boron containing compound (e.g., a borane) which dissociates to free the tertiary amine groups when Part 1 and Part 2 are contacted and which facilitates the desired cure properties may be used in the disclosed compositions. The one or more blocked amine groups may contain a boron containing compound or boron containing group for each available tertiary amine and each available secondary ketimine. The amine containing compound may have an aromatic or cycloaliphatic structure with one or more pendant amine groups (e.g., one or more tertiary amines or one or more secondary ketimines) or aromatic or cycloaliphatic structures with one or more nitrogen atoms (preferably tertiary amines and/or secondary ketimines) incorporated into the ring structures. The amine containing compound may contains an aromatic ring wherein the amine group (e.g., the tertiary amine or secondary ketimine) is disposed on an alkyl group bound to the aromatic ring. The amine containing compound may contain one or more tertiary amines. The amine containing compound may contain one or more heteroatoms other than nitrogen, for example oxygen or oxygen containing functional groups. The amine containing compound may contain a cyclic amidine structure. Exemplary blocked compounds correspond to one of the formulas (e.g., association complexes where the amine containing compound is shown on the left and is associated with the boron containing compound shown on the right of each associ

wherein B represents Boron;

H represents Hydrogen;

X is independently in each occurrence a halogen, alkoxy, carboxylate or acetate group; R is independently in each occurrence a lower alkyl group;

R ² is independently in each occurrence one or more cyclic aliphatic or aromatic rings, which may contain one or more hydrocarbyl groups bonded to the one or more rings and one or more heteroatoms in the cyclic rings or the hydrocarblyl groups, arranged such that the nitrogen atom is tertiary, has three bonds to it;

R ³ is independently in each occurrence a hydrocarbyl group which may contain one or more heteroatoms; R ⁴ is independently in each occurrence a lower alkyl group;

a is independently in each occurrence an integer of from 1 to 3;

b is independently in each occurrence an integer of from 0 to 2;

c is independently in each occurrence an integer of from 0 to 1 ;

wherein either or both of b or c are 0;

d is independently in each occurrence an integer of 0 to 2; and

e is independently in each occurrence an integer of from 1 to 3.

The boron containing compound utilized to block the tertiary amine may be any compound including a boron atom which will dissociate from the amine group (i.e., the tertiary amine and/or the secondary ketimine) in the presence of a mixture of isocyanate reactive compounds and isocyanate functional compounds. Exemplary boron containing compounds for blocking the amine group include a borane and a substituted borane. Preferably each tertiary amine and each secondary ketimine group capable of forming an association with a boron containing compound is blocked. The borane and the substituted boranes are trivalent and may have one or more of hydrogen atoms, halogen atoms, lower alkyl groups, alkoxy groups, carboxylate groups and acetate groups bonded to the Boron atom, provided at least one hydrogen is bonded to the boron atom. Two hydrogen atoms may be bonded to the boron atom. Three hydrogen atoms may be bonded to the boron atom. The lower alkyl group may be a C _1-6 lower alkyl group, a C _1-4 lower alkyl group or methyl or ethyl. The borane or substituted borane may correspond to the formula:

B(H)a(X) (R)c wherein B, H, X, R, a, b, and c are as previously described, a may be independently in each occurrence an integer of from 2 to 3, or 3. B may be independently in each occurrence an integer of from 0 to 1 ; and c may be independently in each occurrence an integer of from 0 to 1 wherein one or both of b and c must be 0. R may be separately in each occurrence a C _1-6 lower alkyl group. R may be separately in each occurrence a C _1-4 lower alkyl group. R may be separately in each occurrence methyl or ethyl.

[0036] The amine containing compound blocked by the boron containing compound may include any amine group that is a tertiary amine group or a secondary ketimine group, that when unblocked can catalyze the reaction of isocyanate groups with isocyanate reactive groups at ambient temperatures. The amine containing compound may have an aromatic or cycloaliphatic structure with one or more pendant amines or aromatic or cycloaliphatic structures with one or more nitrogen atoms incorporated into the ring structures. The amine containing compound may contain an aromatic ring wherein the amine is disposed on an alkyl group bound to the aromatic ring. The amine containing compound may have a cyclic amidine structure. The amine containing compound may contain one or more heteroatoms other than nitrogen, for example oxygen or oxygen containing functional groups. The tertiary amine may contain 1 or more tertiary amino groups. The tertiary amine may contain 6 or less tertiary amino groups, 4 or less tertiary amino groups or 3 or less tertiary amino groups. The tertiary amine may contain 1 to 3 amino groups or 2 to 3 tertiary amino groups. The tertiary amine may c s:

wherein R ² , R ³ , R ⁴ , d and e are as previously described. R ² may form a bicyclic ring which may contain an unblocked sterically hindered tertiary amine. R ³ may be a C ₆ -2o hydrocarbyl group. R ³ may be a C ₆ -2o aryl or alkaryl group. R ³ may be a C M ₅ alkaryl group. R ³ may be trialkyl benzene, triethyl benzene or trimethyl benzene. Where R ³ is trialkyl benzene the tertiary amines may be bonded to the alkyl groups, for example such tertiary amine may be N,N-dialkyl- 1 , 3, 5-triethyl benzene or N,N-dialkyl-1 , 3, 5-trimethyl benzene. R ⁴ may be separately in each occurrence a C _1-6 lower alkyl group. R ⁴ may be separately in each occurrence a C i _-4 lower alkyl group. R ⁴ may be separately in each occurrence methyl or ethyl, e may be an integer of from 1 to 6, 1 to 4, 1 to 3 or 2 to 3. d may be 1 or 2 or 2. Exemplary tertiary amines include 1 ,8-diazabicycloundec-7-ene (DBU), 1 ,5-Diazabicyclo[4.3.0]non-5-ene (DBN) or trisl ,3,5- (2(N,N-dimethyl amino) ethyl) benzene, DABCO (1 ,4-diazabicyclo[2.2.2]octane) , pyridine, and 4-methylmorpholine, 1-methylimidazole and the like.

[0037] The amine containing compound blocked by the boron containing compound are present in a sufficient amount such that when unblocked they can catalyze the reaction of isocyanate groups with isocyanate reactive groups at ambient temperatures. The amine containing compound and/or the blocked compound may be present in Part 2, the polyol component, in an amount based on the weight of Part 2 of about 0.05 percent by weight or greater, about 0.10 percent by weight or greater or about 0.20 percent by weight or greater. The amine containing compound and/or the blocked compound may be present in Part 2, the polyol component, in an amount based on the weight of Part 2 of about 5.0 percent by weight or less, about 2.0 percent by weight or less or about 1.0 percent by weight or less.

[0038] Part 2, polyol component, may contain one or more latent room temperature organometallic catalysts. A latent room temperature organometallic catalysts is a catalyst that functions to catalyze the reaction of the nucleophiles (polyols, polyamines) present in the polyol component with the isocyanates present in the isocyanate component. The latent organometallic catalyst may show delayed action. The latent room temperature catalysts may exhibit accelerated catalytic activity when exposed to temperatures at a temperature of 40 °C or greater. Any latent room temperature organometallic catalysts which provides good open time, acceptable initial lap shear strengths and which maintains an acceptable level of reactivity after partial curing and storage may be utilized. Exemplary classes of latent room temperature organometallic catalysts contain tin, zinc or bismuth. Exemplary latent room temperature organometallic catalysts include zinc alkanoates, bismuth alkanoates, dialkyltin alkanoates, dialkyl tin mercaptides, dialkyl tin bis(alkylmercaptoacetates), dialkyltin thioglycolates or mixtures thereof. Exemplary latent room temperature organometallic catalysts include zinc neoalkanoates, bismuth neoalkanoates, dialkyltin neoalkanoates, dialkyl tin mercaptides, dialkyl tin bis(alkylmercapto acetates), dialkyltin thioglycolates or mixtures thereof. The latent room temperature organometallic catalysts may be dialkyl tin mercaptides, dialkyl tin bis(alkylmercapto-acetates), dialkyltin thioglycolates or mixtures thereof. The latent room temperature organometallic catalysts may be dialkyltin thioglycolates or mixtures thereof. The alkyl groups on the latent room temperature organo-metallic catalysts may be any alkyl groups of about 1 or more carbon atoms or 4 or greater carbon atoms. The alkyl groups on the latent room temperature organometallic catalysts may be any alkyl groups of about 20 or less carbon atoms or 12 or less carbon atoms. Exemplary alkyls groups include methyl, butyl, octyl and dodecyl groups. The latent room temperature organometallic catalysts may be present in an amount sufficient to provide good open time, acceptable initial lap shear strengths and which maintains an acceptable level of reactivity after partial curing and storage. The latent room temperature organometallic catalysts may be present in an amount of about 0.005 percent by weight or greater based on the weight of part 2, about 0.01 percent by weight or greater, about 0.020 percent by weight or greater, or about 0.030 percent by weight or greater. The latent room temperature organometallic catalysts may be present in an amount of about 1.0 percent by weight or less based on the weight of the part 2, about 0.080 percent by weight or less, about 0.070 percent by weight or less or about 0.050 percent by weight or less. These amounts are based on active catalyst, and ignore the mass of solvents or other materials as may be present in a commercially available catalyst product.

[0039] Part 2 component may contain compounds having primary and/or secondary amino groups. Exemplary compounds having primary and/or secondary amino groups include polyoxyalkylene polyamines having 2 or greater amines per poly-amine, 2 to 4 amines per polyamine, or 2 to 3 amines per polyamine. The polyoxyalkylene poly-amines may have a weight average molecular weight of about 200 or greater or about 400 or greater. The polyoxyalkylene polyamine may have a weight average molecular weight of about 5,000 or less or about 3,000 or less. Exemplary polyoxyalkylene polyamines are JEFFAMINE™ D-T-403 polypropylene oxide triamine having a molecular weight of about 400 and JEFFAMINE™ D-400 polypropylene oxide diamine having a molecular weight of about 400. The compounds having primary and/or secondary amino groups are present in a sufficient amount to prevent the composition from sagging once mixed and applied. The compounds having primary and/or secondary amino groups may be present in part 2 in an amount of about 0.2 percent by weight or greater, about 0.3 percent by weight or greater or about 0.5 percent by weight or greater. The compounds having primary and/or secondary amino groups may be present in part 2 in an amount of about 6 percent by weight or less, about 4 percent by weight or less or about 2 percent by weight or less.

[0040] Part 2 may further include one or more optional components. Part 2 may contain at least one particulate filler; however, if a filler is present, it constitutes no more than about 80 weight percent of the total weight of Part 2. The filler may constitute about 25 weight percent or greater of Part 2, or about 30 weight percent or greater. The filler may constitute about 80 weight percent or less of Part 2, about 60 weight percent or less or about 50 weight percent or less. The particulate filler is in the form of particles having a size of about 50 nm to about 100 μηι. The fillers may have a particle size (d50) of about 250 nm or greater, about 500 nm or greater or about 1 μηι or greater. The fillers may have a particle size (d50) of about 50 μηι or less, about 25 μηι or less or about 10 μηι or less. Particles sizes are conveniently measured using dynamic light scattering methods, or laser diffraction methods for particles having a size below about 100 nm. The particulate filler is a solid material at room temperature, is not soluble in the other ingredients of the polyol component or in the polyisocyanate component or any ingredient thereof. The filler is a material that does not melt, volatilize or degrade under the conditions of the curing reaction between the isocyanate reactive and isocyanate functional components. The filler may be, for example, an inorganic filler such as glass, silica, boron oxide, boron nitride, titanium oxide, titanium nitride, fly ash, calcium carbonate, various alumina- silicates including clays such as wollastonite and kaolin, metal particles such as iron, titanium, aluminum, copper, brass, bronze and the like; thermoset polymer particles such as polyurethane, cured particles of an epoxy, phenol-formaldehyde, or cresol-formaldehyde resin, crosslinked polystyrene and the like; thermoplastics such as polystyrene, styrene-acrylonitrile copolymers, polyimide, polyamide-imide, polyether ketone, polyether-ether ketone, polyethyleneimine, poly(p-phenylene sulfide), polyoxymethylene, polycarbonate and the like; and various types of carbon such as activated carbon, graphite, carbon black and the like. In some embodiments, the particulate filler excludes carbon particles. The particles in some embodiments have an aspect ratio of about 5 or less, about 2 or less, or about 1.5 or less. Some or all of the filler particles can be grafted onto one or more of the polyether polyol(s) that Part 2.

[0041] Another optional ingredient is one or more dispersing aids, which wet the surface of the filler particles and help them disperse into theisocyamnate reactive component, such as polyether polyol(s). These may also have the effect of reducing viscosity. Among these are, for example, various dispersing agents sold by BYK Chemie under the BYK, DISPERBYK and ANTI-TERRA-U tradenames, such as alkylammonium salt of a low-molecular-weight polycarboxylic acid polymer and salts of unsaturated polyamine amides and low-molecular acidic polyesters, and fluorinated surfactants such as FC-4430, FC-4432 and FC-4434 from 3M Corporation. Such dispersing aids may constitute, for example, up to 2 weight percent, preferably up to 1 weight percent, of Part 2.

[0042] Another useful optional ingredient of part 2 is a desiccant such as fumed silica, hydrophobically modified fumed silica, silica gel, aerogel, various zeolites and molecular sieves, and the like. One or more desiccants may constitute about 1 percent by weight or greater based on the weight of part 2 and about 5 weight percent or less, or about 4 weight percent or less of Part 2, and may be absent from the polyol component.

[0043] The Part 2 may further include one or more additional isocyanate-reactive compounds, different from those previously described, and which do not contain amine hydrogen atoms. If any such additional isocyanate-reactive compound(s) are present, they may constitute no more than 10 percent, no more than 5 percent or no more than 2 percent of the weight of the polyol component. Examples of such additional isocyanate-reactive compounds include, for example, one or more polyester polyols; one or more polyether polyols containing at least 50 weight percent polymerized ethylene oxide; one or more polyether polyols having a hydroxyl equivalent weight of 100 to 499; and one or more hydroxy-functional crosslinkers having three or more isocyanate-reactive groups per molecule and a hydroxyl equivalent weight of up to 499.

[0044] The composition may be non-cellular, and for that reason, Part 2 may contain about 0.5% by weight or less, about 0.1 %, by weight or less of organic compounds having a boiling temperature of 80°C or below, and about 0.1 % by weight or less, or about 0.05% by weight or less, of water and/or other chemical blowing agents that produce a gas under the conditions of the curing reaction.

[0045] Part 2 may contain about 10 weight percent or less, about 5 weight percent or less, or about 1 weight percent or less, of a plasticizer such as a phthalate, terephthalate, mellitate, sebacate, maleate or other ester plasticizer, a sulfonamide plasticizer, a phosphate ester plasticizer, soy methyl ester, rape seed oil methyl ester or a polyether di(carboxylate) plasticizer. Such a plasticizer may be absent from the polyol component.

[0046] The two-part adhesive disclosed may comprises one or more phenol blocked cyclic tertiary amines or secondary ketimines. Any phenol blocked cyclic tertiary amine or secondary ketimine which provides good open time, acceptable initial lap shear strengths and which maintains an acceptable level of reactivity after partial curing and storage may be utilized.

Exemplary phenol blocked cyclic tertiary amines or phenol blocked cyclic secondary ketimines include phenol blocked cyclic amidine catalysts, aromatic or cycloaliphatic structures with pending amines or aromatic or cycloaliphatic structures with nitrogens incorporated into the ring structures and the like. Exemplary cyclic amidine catalysts include 1 ,8-diazabicycloundec-7- ene (DBU) or 1 ,5-Diazabicyclo[4.3.0]non-5-ene (DBN) and the like. The blocking agent may be a phenolic compound such as phenol itself or a substituted phenol. The phenol-blocked cyclic amidine catalyst can be incorporated into either the polyol component or the polyisocyanate component. The phenol blocked cyclic amine (tertirary amine or secondary ketimine) catalyst may be present in an amount sufficient to provide good open time, acceptable initial lap shear strengths and which maintains an acceptable level of reactivity after partial curing and storage. The phenol blocked cyclic tertiary amine or secondary ketimine catalyst may be present in an amount of about 0.01 percent by weight or greater based on the weight of the polyol or polyisocyanate component or about 0.015 percent by weight or greater. The phenol blocked cyclic tertiary amine or secondary ketimine catalyst may be present in an amount of about 2.0 percent by weight or less based on the weight of the polyol or polyisocyanate component, about 1.0 percent by weight or less or about 0.025 percent by weight or less.

[0047] The two-part adhesive disclosed may comprise one or more carboxylic acid blocked cyclic tertiary amine or secondary ketimines. Any carboxylic acid blocked cyclic tertiary amine or secondary ketimine which provides good open time, acceptable initial lap shear strengths and which maintains an acceptable level of reactivity after partial curing and storage may be utilized. Exemplary carboxylic acid blocked cyclic tertiary amines and secondary ketimines include carboxylic acid blocked cyclic amidine corn-pounds, aromatic or cycloaliphatic structures with pending amines or aromatic or cycloaliphatic structures with nitrogens incorporated into the ring structures and the like. Exemplary cyclic amidine catalysts include 1 ,8-diazabicycloundec-7-ene (DBU), or 1 ,5-Diaza-bicyclo[4.3.0]non-5-ene (DBN) and the like. The blocking agent may be one or more aliphatic carboxylic acids having 1 to 24 carbon atoms, especially 1 to 8 carbon atoms. The carboxylic acid-blocked tertiary amines can be incorporated into either the polyol component or the polyisocyanate component. The carboxylic acid blocked cyclic tertiary amines and carboxylic acid blocked cyclic secondary ketimine may be present in an amount sufficient to provide good open time, acceptable initial lap shear strengths and which maintains an acceptable level of reactivity after partial curing and storage. The carboxylic acid blocked cyclic tertiary amines and secondary ketimines may be present in an amount of about 0.01 percent by weight or greater based on the weight of the polyol or polyiscyanate component or about 0.015 percent by weight or greater. The carboxylic acid blocked cyclic tertiary amines and secondary ketimines may be present in an amount of about 2.0 percent by weight or less based on the weight of the polyol or polyiscyanate component, about 1.0 percent by weight or less or about 0.025 percent by weight or less.

[0048] Part 1 , polyisocyanate component, and Part 2, polyol component, may be formulated such that when equal volumes of the components are provided, the isocyanate index may be 1.0 to 1.8, 1.1 to 1.8, or 1.15 to 1.65. "Isocyanate index" is the ratio of the number of isocyanate groups in Part 1 , the polyisocyanate component to the number of isocyanate- reactive groups in Part 2, the polyol component. The isocyanate index, at a 1 : 1 volume ratio, may be 1.15 to 1.65.

[0049] Disclosed is a process for bonding two substrates. Part 1 and Part 2 are mixed to form the mixed adhesive. The ratio of these materials is generally sufficient to provide an isocyanate index as disclosed herein. The mixed adhesive is formed into an adhesive layer between and in contact with the two substrates. An adhesion promoter may be applied to one or both of the substrates prior to contacting the substrate(s) with the adhesive. The adhesive layer is then cured between and in contact with the two substrates to form a layer of cured adhesive bonded to each of the two substrates.

[0050] The methods used to mix Part 1 with Part 2 to form the adhesive layer and cure the adhesive are not critical and a variety of apparatus can be used to perform these steps. The parts can be mixed and applied to the substrates manually, in various types of batch apparatus, and/or using various sorts of automated metering, mixing and dispensing equipment.

[0051] The parts often will react spontaneously upon mixing at room temperature (about 23°C) and cure without the need to heat the adhesive to a greater temperature. Curing may be effected by simply mixing the components at a temperature of, for example, 0 to 50°C, 15 °C to 50 °C, 0 °C to 35°C, 15 °C to 35 °C, or 20 °C to 35 °C and allowing the components to react at that temperature.

[0052] Heating can be applied to the adhesive to obtain a more rapid cure. The two parts can be heated separately and then mixed and cured, with or without further applied heat. Alternatively, the polyol and isocyanate components can be mixed at a lower temperature, such as 0 to 35°C and then heated to a higher cure temperature. The substrate can be heated before applying the adhesive if desired. If an elevated temperature is used in the curing step, such a temperature may be, for example, about 36 °C or greater, or about 50 °C or greater. Such a temperature may be, for example, about 150°C or less, or about 130°C or less.

[0053] A layer of the two-component polyurethane adhesive may be formed at a bondline between two substrates to form an assembly. The adhesive layer may then at least partially cured at the bondline by applying infrared radiation to the assembly. Infrared radiation may be applied, for example, until the temperature of the adhesive layer reaches about 80°C or greater, or about 90°C or greater, or about 150°C or less, or about 130°C or less. The assembly so heated may be maintained under infrared radiation until the adhesive layer has been exposed to such temperatures for a period of 5 seconds or more to effect the partial or complete cure. For example, the infrared radiation may be continued until the temperature of adhesive layer is 80 to 150°C, preferably 90 to 130°C, for 5 to 60 seconds, 5 to 45 seconds, for 10 to 30 seconds or for 10 to 20 seconds, at which time the exposure to infrared radiation is discontinued.

[0054] If only a partial cure is performed by applying infrared radiation, the partial curing can be either or both of two types. In one type of partial curing, the entire adhesive layer is cured, but only partially. The partial curing may proceed to at least to the gel point, at which a three- dimensional polymeric network is formed in the adhesive layer by the curing of the components. In another type of partial curing, only one or more predetermined, localized portions of the adhesive layer at the bondline are cured. This produces an adhesive layer having at least partially cured portions and portions that have undergone little or no cure. The predetermined, localized portions of the adhesive layer may constitute, for example, 5 to 80%, 5 to 50% or 5 to 25% of the total area of the adhesive layer. Subsequent to the partial curing step, the uncured or only partially cured portions of the adhesive layer then are cured further to form a fully-cured adhesive. The subsequent step of completing the cure can be done at approximately room temperature (such as from 15 to 35°C) or an elevated temperature such as greater than 35°C to 80°C.

[0055] A two-step curing process as just described is useful in a variety of manufacturing, building and construction, and in-field assembly and repair applications. By performing only a partial cure by applying infrared radiation, a rapid bonding of the adhesive to the substrate can be obtained in a very short time, often a matter of 10 seconds to 2 minutes. The bonded parts can be handled after 1 hour or greater from partial cure, after about 10 minutes or greater after partial cure, about 3 minutes or greater after partial cure or about 1 minute or greater after partial cure. This initial bond is often robust enough that the assembly can withstand further handling. Further handing may include, for example, transporting the assembly to a downstream work station, and further manufacturing steps which might include joining the assembly to one or more other components, various shaping and/or machining steps, the application of a coating, and the like. The completion of the cure can take place during and/or after such additional handling steps. Often, the adhesive will fully cure without exposing it to elevated temperature, infrared radiation or other energy source, due at least in part to the catalytic action of the organometalic catalyst. The acid-blocked cyclic amidine catalyst may deblock during the infrared heating stage, to produce an active catalyst that promotes the cure during the subsequent curing step, even if that subsequent step is performed without additional applied energy.

[0056] The substrates are not limited. They may be a metal, a metal alloy, an organic polymer, a lignocellulosic material such as wood, cardboard or paper, a ceramic material, various types of composites, or other materials. Carbon fiber reinforced plastic is a substrate of particular interest. The substrates in some embodiments are vehicular parts or vehicular sub-assemblies that are adhered together with a cured adhesive composition disclosed. The substrates may be individual plies that are glued together using the adhesive to form a multilayer laminate. The substrates may be building members.

[0057] Other components commonly used in curable compositions may be used in the compositions disclosed. Such materials are well known to those skilled in the art and may include ultraviolet stabilizers and antioxidants and the like. The compositions may also contain durability stabilizers known in the art. Exemplary durability stabilizers are alkyl substituted phenols, phosphites, sebacates and cinnamates. One class of durability stabilizers includes organophosphites. The organophosphites may be present in a sufficient amount to enhance the durability of bond of the adhesive composition to the substrate surface. Such phosphites are disclosed in Hsieh et al. US 7,416,599 column 10, line 47 to Column 11 line 25, incorporated herein by reference. Exemplary organophosphites include poly(dipropyleneglycol) phenyl phosphite (avail-able from Dover Chemical Corporation under the trademark and designation DOVERPHOS 12), tetrakis isodecyl 4,4'iso-propylidene diphosphite (available from Dover Chemical Corporation under the trademark and designation DOVERPHOS 675), and phenyl diisodecyl phosphite (available from Dover Chemical Corporation under the trademark and designation DOVERPHOS 7). The organophosphite may be present in the composition in an amount of about 0.1 percent by weight or greater or about 0.2 percent by weight or greater based on the weight of the composition. The organophosphite may be present in the composition in an amount of about 1.0 percent by weight or less or about 0.5 percent by weight or less based on the weight of the composition.

[0058] The composition may be formulated by blending the components together using means well known in the art. The components may be blended in a suitable mixer. Such blending may be conducted in an inert atmosphere in the absence of oxygen and atmospheric moisture to prevent premature reaction

[0059] The compositions disclosed may be formulated to provide an open time of about 5 minutes or greater, 7 minutes or greater, about 8 minutes or greater or about 9 minutes or greater. The two part adhesive compositions may be formulated to provide an open time of about 30 minutes or less, about 20 minutes or less or about 15 minutes or less. "Open time" is understood to mean the time after application of the composition to a first substrate until it starts to become a high viscous paste and is not subject to deformation during assembly to conform to the shape of the second substrate and to adhere to it. Open time may be measured by rheology reactivity wherein the rheology reactivity is about 500 seconds or greater or about 600 seconds or greater.

[0060] The compositions disclosed may exhibit a lap shear strength after 1 hour room temperature cure of greater than 0.6 MPa, about 0.8 MPa or greater or about 1 MPa or greater. The compositions may exhibit a low loss in Lap shear strength after storage of one month, for example less than 42 percent reduction is lap shear strength or about 40 percent or less loss in lap shear strength.

[0061] Molecular weights as described herein are number average molecular weights which may be determined by Gel Permeation Chromatography (also referred to as GPC). For polyurethane prepolymers, it is also possible to calculate approximate number average molecular weight from the equivalent ratio of the isocyanate compounds and of the polyol compounds with which they are reacted as known to the persons skilled in the art.

[0062] The compositions disclosed may further comprise any one or more of the features described in this specification in any combination, including the preferences and examples listed in this specification, and includes the following features. [0063] The methods disclosed may further comprise any one or more of the features described in this specification in any combination, including the preferences and examples listed in this specification, and includes the following features.

ILLUSTRATIVE EMBODIMENTS

[0064] The following examples are provided to illustrate the disclosed compositions, but are not intended to limit the scope thereof. All parts and percentages are by weight unless otherwise indicated.

[0065] Ingredients

Voranol 4701 Polyether Triol has a functionality of 3, an equivalent weight of 1652 and a percent primary hydroxyl of 74.

Voranol 4703 polyether triol has a functionality of 3, an equivalent weight of 1652 and a percent primary hydroxyl of 74

Voranol 360 polyether polyol is a 4.5 functional sucrose/glycerine initiated polyether polyol having a functionality of about 4.9, a hydroxyl equivalent weight of about 156 and a primary hydroxyl percentage of 78.5.

Specflex 630 is a polyether polyol having a functionality of 4.2, a hydroxyl equivalent weight of about 1810 and 0 percent primary hydroxyl groups. Polyol A is a polypropylene homopolymer with an average molecular weight of 1000 g/mol molecular weight and a OH number of approximately 55 mg KOH/g.

Polyol B is nominally trifunctional a glycerin initiated ethylene oxide based propoxylated triol with an average molecular weight of 1800 g/mol molecular weight and an OH number of approximately 35 mg KOH/g.

1 ,4-butane diol.

PEG 2000 polyethylene glycol is a difunctional polyethylene glycol having a molecular weight of about 2000.

The Aminated Polyether is a 400 g/mol, difunctional poly(propylene oxide) terminated in primary amine groups, sold as Jeffamine™ D-400 by Huntsman Corporation.

The Aliphatic Polyisocyanate is a commercially available product based on hexamethylene diisocyanate, having an isocyanate equivalent weight of 193 (Desmodur™ N3400 from Bayer Material Sciences).

The Liquid MDI is a commercially available modified MDI product having an isocyanate functionality of about 2.2 and equivalent weight of about 143.

Polymeric MDI is a reaction product of methylene diphenyl isocyanate having an isocyanate equivalent weight of 134, a functionality of 2.7and an NCO content of 31.4. Modified Pure MDI is a modified methylene diisocyanate having an isocyanate equivalent weight of 180 a functionality of 2.0 and an isocyanate content of about 26.3. Prepolymer B is an isocyanate functional prepolymer comprising the reaction product of an polyetherpolyol with MDI .

Molecular Sieve Paste is a 4A zeolite_

Fumed Silica fumed silica surface treated with polydimethyl siloxane avaialbe from Evonik Industries under the Trademark AEROSIL™ ^R 202.

[0066] Prepolymer Preparation

The prepolymer is prepared by combining 33 parts by weight of liquid MDI and 41.6 parts of polymeric MDI and heating the resulting mixture to 90 °C for 30 minutes. Thereafter 25 parts by weight of PEG 2000 polyether polyol is added and the resulting mixture is heated under vacuum for 90 minutes at 90 °C.

[0067] Borane Blocked 1 ,8-Diazabicyclo[5.4.0]undec-7-ene (Catalyst 2) Preparation

To 4.7 ml_ 1 ,8-Diazabicyclo[5.4.0]undec-7-ene (d = 1.018 g/mL, 152.24 g/mol, 31 mmol) in 75 ml_ tetrahydrofuran (THF) in a glovebox, 35 mL 1.0 M BH3-THF (35 mmol) is added slowly with stirring. After 1 hour, solution is removed from the glovebox, cooled in an ice bath, and water slowly added to quench (about 30 mL). The resulting mixture is extracted with dichloromethane (50 + 30 + 30 mL), washed with water (2x30 mL), and the solvent is allowed to evaporate, resulting in -1.5 g of oil (29% yield). This catalyst is referred to as DBU-BH3 and is by the following formula (where the arrow indicates blocking by the boron):

BH ₃

[0068] Borane Blocked 1 ,5-Diazabicyclo[4.3.0]non-5-ene (Catalyst 3) is prepared as described in the previous example This catalyst is referred to as DBN-BH3 and is represented wing formula:

BH ₃

[0069] Borane Blocked Tris-3BH (Catalyst 4) is prepared as described previously. This catalyst is referred to as Tris-3 BH3 and is represented by the following formula:

[0070] Catalyst A is a 1 % solution of dioctyltin dineodecanoate cocatalyst..

Catalyst B is a phenol-blocked 1 ,8-diazabicycloundec-7-ene catalyst that contains about 50% by weight active material. Catalyst C is Dioctyl tin mercaptide avaialbe from Momentive under the designation UL 29 catalyst.

Reactivity Testing

Two polyol formulations are prepared by mixing the ingredients listed in Table 1.

Table 1. Polyol formulations used in the reactivity testing.

[0071 ] 4 samples are prepared from Polyol A wherein each sample contains 0.05 or 0.1 percent by weight of one of the following catalysts, Catalyst B, DBN-BH3, DBU-BH3 and Tris-3 BH3. All samples contain 1 % solution of dioctyltin dineodecanoate cocatalyst, Catalyst A. 12.6 parts of each Polyol A formulation is combined with 7.4 parts of the isocyanate functional prepolymer. Data for the viscosity over time in seconds is recorded. This Data is illustrated in Figure 1. In Figure 1 triangles represent samples with Catalyst B as a comparative example, squares represent samples containing catalyst (DBU-BH3), circles represent samples containing catalyst (DBN-BH3), and diamonds represent samples containing catalyst (Tris- 3BH3).

[0072] 4 samples are prepared from Polyol B wherein each sample contains 0.05 or 0.1 percent by weight of one of the following catalysts, Catalyst B, DBN-BH3, DBU-BH3 and Tris-3 BH3. All samples contain 1 % solution of dioctyltin dineodecanoate cocatalyst, Catalyst A. 1 1.8 parts of each Polyol B formulation is combined with 8.2 parts of the isocyanate functional prepolymer. Data for the viscosity over time in seconds is recorded. This Data is illustrated in Figure 2. In Figure 2 triangles represent samples with Catalyst B as a comparative example, squares represent samples containing catalyst (DBU-BH3), circles represent samples containing catalyst (DBN-BH3), and diamonds represent samples containing catalyst (Tris- 3BH3).

[0073] Figures 1 and 2 illustrate Comparison of DBU-PhOH to three borane complexes, indicated by viscosity over time at 30 °C. Data for reaction of 12.6 g Polyol A with 7.4 g isocyanate composition. Triangles represent DBU-PhOH as a comparative example, squares catalyst 2 (DBU-BH ₃ ), circles catalyst 3 (DBN-BH ₃ ), and diamonds catalyst 4 (Tris-3BH ₃ ). Each reaction also included 40 mg of a 1 % solution of dioctyltin dineodecanoate cocatalyst. Comparison of DBU-PhOH to three borane complexes, indicated by viscosity over time at 30 °C. Data for reaction of 1 1 .8 g Polyol B with 8.2 g isocyanate composition. Each reaction also included 40 mg of a 1 % solution of dioctyltin dineodecanoate cocatalyst..

[0074] Application Testing

In the application testing the polyol formulation is provided in Table 2.

[0075] Table 2

PolC masterbatch Parts bw

Voranol 4610 45.100

1-4 Butandiol 4.300

Voranol 280 4.000

Catalyst C 0.045

Polestar 200R 40.990

Molsieb 4A 4.000

Aerosil R202 1.500

The polyol master batch is used to prepare several polyol samples as listed

The polyisocyanate part is described in Table 4.

Table 4. Isocyanate component used for application test

Parts bw

Carbon Black 18.000

Polyiscyanate 5.000

Plasticizer 6.000

Modified pure MDI 28.500

Prepolymer B 44.500

[0079] The various polyol samples are contacted with the isocyanate composition in a volume ratio of 1 to 1. The samples are tested for reactivity, open time, TFT (Tack free time), 1 hour lap shear strength and Intial IR Lap shear strength according to the following procedures. The results are compiled in Table 5.

[0080] Open time. An adhesive bead of 30 - 50 cm length is manually extruded onto a polyethylene foil. Manual application of 2K polyurethane adhesives was done from a double cartridge application guns, as. e.g. Kroger TS 400 with a mounted static mixer unit 8mm or 10 mm diameter and 24 mixing elements and an application pressure of min. 6 bar. The applied adhesive bead is compressed successively with a wooden spatula until no adhesive sticks any longer to the wooden surface. Two measurement times are recorded: 1) open time: time that the adhesive cannot be smoothly compressed and 2) Tack-free time (TFT): time that the adhesive doesn't stick to the wooden surface.

[0081] Reactivity. The reactivity of the 2K PU adhesive is measured by rheology in oscillating mode with a parallel plate 20 mm diameter, 1 mm plate distance set-up. The measurements is performed at 10 Hz with a constant deformation of 0.062%. The complex viscosity is plotted against the time and the time at which the slope of viscosity is changed more than 30° is considered to be the reactivity.

[0082] Shear strength. Shear strengths measurements are performed according to DIN

EN 527 on a suitable device, e.g. shear strength device Zwick 1435 with a FHM 8606.00.00 or 8606.04.00 mounting device. E-coat substrates are Cathoguard 500 e-coated steel panels with of 100x25x0.8mm. E-coated substrates are cleaned with BETACLEANTM 3350 (heptane). The flash off time of the solvent after cleaning prior to adhesive application is 5 minutes. CFRP substrates are VORAFORCETM grade panels from DOW CFRP VORAFORCETM 5300 with a dimension of 100x45x2.2 mm. CFRP substrates are grinded or used without cleaning or mechanical pretreatment. Grinding is perfromed manually, using a 320 grinding pad on wet CFRP panels until homogeneous optical appearance is achieved. Panels are successively dried 8h at 80°C. Adhesive bond dimension of 10x25x1.5 mm are used for the lap shear specimens. Lap shear specimens are tested after 1 hour curing time at 23°C/50% relative humidity, (reported as 1-hour LS) or respectively after described heat accelerated curing process.

[0083] Heat accelerated curing. For heat accelerated curing, the assembled CFRP-

CFRP lap shear specimens are placed after assembly in an I R curing equipment. Lap shear specimens are built up with a bond height of 1.5 mm and an overlap area of 45 x 10 mm. The CFRP substrate, exposed to the IR source is heated during a 120 sec curing process in such a way, that 100 - 110°C adhesive temperature is reached for a time period of 10 - 20 sec heating profile. The results are recorded and reported as "initial IR LS".

[0084] The viscosity build-up of each of the samples is illustrated in Figure 3. For the figure which example have which catalyst package. Table 5. Application Test Results for formulations with borane complexes as catalyst

[0085] The reactivity testing illustrates that that adhesives have certain open times.

Reactivity is a rheological method to measure open time

[0086] Parts by weight as used herein refers to 100 parts by weight of the composition specifically referred to. Any numerical values recited in the above application include all values from the lower value to the upper value in increments of one unit provided that there is a separation of at least 2 units between any lower value and any higher value. These are only examples of what is specifically intended and all possible combinations of numerical values between the lowest value, and the highest value enumerated are to be considered to be expressly stated in this application in a similar manner. Unless otherwise stated, all ranges include both endpoints and all numbers between the endpoints. The use of "about" or "approximately" in connection with a range applies to both ends of the range. Thus, "about 20 to 30" is intended to cover "about 20 to about 30", inclusive of at least the specified endpoints. The term "consisting essentially of" to describe a combination shall include the elements, ingredients, components or steps identified, and such other elements ingredients, components or steps that do not materially affect the basic and novel characteristics of the combination. The use of the terms "comprising" or "including" to describe combinations of elements, ingredients, components or steps herein also contemplates embodiments that consist essentially of the elements, ingredients, components or steps. Plural elements, ingredients, components or steps can be provided by a single integrated element, ingredient, component or step. Alternatively, a single integrated element, ingredient, component or step might be divided into separate plural elements, ingredients, components or steps. The disclosure of "a" or "one" to describe an element, ingredient, component or step is not intended to foreclose additional elements, ingredients, components or steps.