Epoxy adhesive having improved impact resistance

Abstract

In the preparation of an improved adhesive composition, a first reaction product is prepared by the reaction at an elevated temperature of a) 30 to 50 wt-% of an epoxy resin, solid at room temperature, which was prepared from bisphenol A and/or bisphenol F and epichlorohydrin with an epoxide equivalent weight of 400 to 700, b) 10 to 25 wt-% of an epoxy resin, liquid at room temperature, prepared from bisphenol A and/or bisphenol F and epichlorohydrin with an epoxide equivalent weight of 150 to 220, c) 35 to 50 wt-% amino-terminated polyethylene and/or polypropylene glycols and d) a carboxyl-terminated butadiene-nitrile rubber. The first reaction product is mixed with an acrylate terminated urethane resin, glass microspheres, expandable hollow plastic microspheres and a latent curing agent to make an adhesive composition which is pumpable at room temperature and capable of expansion to about 100% with high impact resistance after curing.

Description

TECHNICAL FIELD

[0001] This invention relates to methods and compositions useful as adhesives and more particularly to making epoxy based adhesives capable of being employed with or without expansion agents.

BACKGROUND

[0002] Numerous compositions and processes are described in the prior art for making and using a wide variety epoxy-based compositions and other resins and additives in an effort to improve expansion, impact resistance and other key properties of adhesives useful in adhering, filling and making composite structures. For example, various patents describe components and resulting composition and uses such as U.S. Pat. Nos. 5,334,654, 6,270,600, 6,332,731, 5,755,468, and 6,015,865. Nevertheless, significant problems remain prior to the present invention in relation to preparing high impact epoxy based adhesives especially when such adhesives are employed in an expanded state. Further, problems have existed in preparing high impact, expandable adhesives which can be flowed to the application site by pumping, for example, at ambient or moderate temperatures.

BRIEF DESCRIPTION OF THE INVENTION

[0003] We have discovered that unexpectedly improved adhesive formulations can be prepared by pre-reacting a polyepoxide resin having at least two 1,2-epoxy groups per molecule with polyoxy alkylene amine and, optionally, an aduct of carboxy terminated butadiene-nitrile rubber (BNR) to produce a pre-reaction product which is then admixed with an acrylate terminated urethane resin as defined herein, preferably the reaction product of an isocyanate terminated urethane prepolymer and an isocyanate reactive acrylate or methacrylate, a latent curing agent, and optionally with fillers, coloring agents, expanding or blowing agents, or other adjuvants of the type known in the art. When applied to a substrate or carrier the adhesive results in a product having improved impact toughness or impact resistance useful in a wide variety of applications.

[0004] In a preferred embodiment, a curable adhesive is formulated which comprises:

[0005] A) a prepolymer reaction mixture of

[0006] (a) epoxy resin or resins prepared from bisphenol A or bisphenol F and epichlorohydrin having an epoxide equivalent weight of from about 150 to about 700,

[0007] (b) an amino-terminated polyalkylene glycol selected from the group consisting of polyethylene and polypropylene glycols, or a carboxyl terminated butadienenitrile resin, or mixtures thereof,

[0008] B) an acrylate-terminated urethane resin and

[0009] C) a latent curing agent.

DETAILED DESCRIPTION OF THE INVENTION

[0010] In a further preferred embodiment, the pre-reaction products useful in producing adhesive compositions of this invention are prepared in accordance with U.S. Pat. No. 6,015,865 which is hereby incorporated by reference in its entirety. In this preferred embodiment the epoxy resin component is obtained by reacting

[0011] a) an epoxy resin which is solid at room temperature and

[0012] b) an epoxy resin which is liquid at room temperature with

[0013] c) linear amino-terminated polyethylene glycols (ATPEG) or linear and/or trifunctional amino-terminated polypropylene glycols (ATPPG), the epoxy resins a) and b) being used in such a quantity that an excess of epoxide groups over the amino groups is ensured.

[0014] At this point mention is made that the components a), b) and c) can, in each case, also be mixtures of compounds of the given type.

[0015] This pre-reaction product can be modified by adding other modified epoxy resins such as:

[0016] i) adducts of dimeric fatty acids having varying molecular weights with epoxy resins of the diglycidyl ether type of bisphenol A or F (DGEBA or DGEBF) (e.g. Epikote® or EPON® 872),

[0017] ii) adducts of carboxyl-terminated butadiene-nitrile rubber (CTBN) (Hycar® 1300X8, 1300X13; Struktol® with DGEBA or DGEBF

[0018] so that, even at high temperatures (up to +90°. C.) and under ageing conditions (corrosion, moisture), they exhibit permanent strength. Preferably 4 to 40, particularly 5 to 25, e.g. 20% of the epoxide equivalents (EEW) of the total epoxy resin component may be replaced by such adducts.

[0019] When reacting the epoxy resins with the ATPEG/ATPPG, an excess of epoxy groups over the amino groups is preferably employed so that the latter react completely with epoxide groups. Typically, there is a 1.5 to 10-fold excess, for example a 3.5-fold excess of EEW over the active hydrogen equivalents (AHEW) of the amines.

[0020] The epoxy based prepolymer is then admixed with an acrylate terminated urethane resin as described herein and a latent curing agent; and formulated according to known methods to prepare an improved curable adhesive for use in expanded or non-expanded applications where high impact resistance is needed.

[0021] The adhesive made according to this invention results in high T-peel and impact peel strength in the temperature range of −40° C. to +90° C. In the cured state, these adhesives display the degree of flexibility which is necessary especially in the manufacture of automobiles and trucks. The flexibility of the resin matrix may be adjusted by using ATPEG or ATPPG of varying functionality (bi- or trifunctional) and variable chain-length, and by varying the ratio of ATPEG/ATPPG to epoxy resin. The impact toughness and flowability at ambient temperatures may be adjusted by varying the ratio of epoxy-based prepolymer to the acrylate functional urethane resin or resins.

[0022] The weight ratio of epoxy prepolymer to acrylate terminated urethane resin is preferably between about 50:1 to 1:1—and most preferably between about 20:1 to 4:1.

[0023] Surprisingly, the curable adhesives made by combining the epoxy based prepolymers which contain at least two 1,2-epoxy groups per molecule and an amino-terminated polyalkylene glycol and or carboxyl terminated butadiene-nitrile rubber with the acrylate functional urethane resins and a latent curing agent are pumpable at ambient temperatures or slightly higher , e.g., between about 10 to about 50 degrees C., preferably between about 20 and about 40 degrees C. and have improved peel strengths both in the expanded and unexpanded cured state over the prior art.

[0024] In general, a large number of polyepoxides having at least two 1,2-epoxy groups per molecule are suitable as epoxy resins for making the pre-polymer reaction product employed in this invention. The polyepoxides may be saturated, unsaturated, cyclic or acyclic, aliphatic, alicyclic, aromatic or heterocyclic polyepoxide compounds. Examples of suitable polyepoxides include the polyglycidyl ethers, which are prepared by reaction of epichlorohydrin or epibromohydrin with a polyphenol in the presence of alkali. Suitable polyphenols therefor are, for example, resorcinol, pyrocatechol, hydroquinone, bisphenol A (bis(4-hydroxyphenyl)-2,2-propane), bisphenol F (bis(4-hydroxyphenyl)methane), bis(4-hydroxyphenyl)-1,1-isobutane, 4,4′-dihydroxybenzophenone, bis(4-hydroxyphenyl)-1,1-ethane, and 1,5-hydroxynaphthalene. Other suitable polyphenols as the basis for the polyglycidyl ethers are the known condensation products of phenol and formaldehyde or acetaldehyde of the novolak resin-type.

[0025] Other polyepoxides that are in principle suitable are the polyglycidyl ethers of polyalcohols or diamines. Those polyglycidyl ethers are derived from polyalcohols, such as ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,4-butylene glycol, triethylene glycol, 1,5-pentanediol, 1,6-hexanediol or trimethylolpropane.

[0026] Other polyepoxides are polyglycidyl esters of polycarboxylic acids, for example reaction products of glycidol or epichlorohydrin with aliphatic or aromatic polycarboxylic acids, such as oxalic acid, succinic acid, glutaric acid, terephthalic acid or a dimeric fatty acid.

[0027] Other epoxides are derived from the epoxidation products of olefinically-unsaturated cycloaliphatic compounds or from natural oils and fats.

[0028] Particular preference is given to the epoxy resins derived by reaction of bisphenol A or bisphenol F and epichlorohydrin, the liquid epoxy resins preferably being based on bisphenol A and having a sufficiently low molecular weight. The epoxy resins that are liquid at room temperature generally have weights of from 150 to about 480; particular preference is given to an epoxy equivalent weight range of from 182 to 350.

[0029] The epoxy resins that are solid at room temperature are likewise obtainable from polyphenols and epichlorohydrin; particular preference is given to those based on bisphenol A or bisphenol F having a melting point of from 45 to 130° C., preferably from 50 to 80° C.

[0030] They differ from the liquid epoxy resins substantially by the higher molecular weight thereof, as a result of which they become solid at room temperature. According to the present invention, the solid epoxy resins have an epoxy equivalent weight of ≧400; particular preference is given to an epoxy equivalent weight of from 450 to about 900.

[0031] There may be used as flexibility-conferring epoxy resins adducts of carboxyl-terminated butadieneacrylonitrile copolymers (CTBN) and liquid epoxy resins based on the diglycidyl ether of bisphenol A. Specific examples are the reaction products of Hycar CTBN 1300 X8, 1300 X13 or 1300 X15 of B. F. Goodrich with liquid epoxy resins. There may also be used the reaction products of amino-terminated polyalkylene glycols (such as those sold under the trademark “JEFFAMINES” by Huntsman Chemical) with an excess of liquid polyepoxides. Such reaction products are disclosed, for example, in U.S. Pat. No. 6,015,865. In principle there may also be used according to the present invention as flexibility-conferring epoxy resins reaction products of mercapto-functional polymers with an excess of polyepoxides. Particular preference is given, however, to the reaction products of polymeric fatty acids, especially of dimeric fatty acids, with epichlorohydrin, glycidol or, especially, the diglycidyl ether of bisphenol A (DGBA).

[0032] Since the curable adhesives of the present invention are preferably one-part or single-component compositions and are to be cured at elevated temperature, they also contain a hardener and/or, in addition, one or more accelerators.

[0033] There may be used as thermally-activatable or latent hardeners for the epoxy resin binder system consisting of components (a), (b) and (c) guanidines, substituted guanidines, substituted ureas, melamine resins, guanamine derivatives, cyclic tertiary amines, aromatic amines and/or mixtures thereof. The hardeners may be involved stoichiometrically in the hardening reaction; they may, however, also be catalytically active. Examples of substituted guanidines are methylguanidine, dimethylguanidine, trimethylguanidine, tetra-methylguanidine, methylisobiguanidine, dimethylisobiguanidine, tetramethylisobiguanidine, hexamethylisobiguanidine, heptamethylisobiguanidine and, more especially, cyanoguanidine (dicyandiamide). Representatives of suitable guanamine derivatives which may be mentioned are alkylated benzoguanamine resins, benzoguanamine resins or methoxymethylethoxymethylbenzoguanamine. For the single-component, thermosetting hot melt adhesives, the selection criterion is, of course, the low solubility of those substances at room temperature in the resin system, so that solid, finely ground hardeners are preferred; dicyandiamide is especially suitable. Good storage stability of the composition is thereby ensured.

[0034] In addition to or instead of the above-mentioned hardeners, catalytically-active substituted ureas may be used. They are especially p-chlorophenyl-N,N-dimethylurea (monuron), 3-phenyl-1,1-dimethylurea (fenuron) or 3,4-dichlorophenyl-N,N-dimethylurea (diuron). In principle, catalytically active tertiary acryl- or alkyl-amines, such as benzyldimethylamine, tris(dimethylamino)phenol, piperidine or piperidine derivatives, may also be used, but they are in many cases too highly soluble in the adhesive system, so that usable storage stability of the single-component system is not achieved. Various imidazole derivatives, preferably solid imidazole derivatives, may also be used as catalytically-active accelerators. Examples which may be mentioned are 2-ethyl-2-methylimidazole, N-butylimidazole, benzimidazole and N-C1 to C12-alkylimidazoles or N-arylimidazoles. Particular preference is given to the use of a combination of hardener and accelerator in the form of so-called accelerated dicyandiamides in finely ground form. The separate addition of catalytically-active accelerators to the epoxy hardening system is thus not necessary.

[0035] The adhesives according to the present invention may also contain known fillers such as the various ground or precipitated chalks, carbon black, calcium magnesium carbonates, barite and, especially, silicate-like fillers of the aluminum magnesium calcium silicate type, for example wollastonite, chlorite.

[0036] When it is desirable to make lightweight structures, the adhesives preferably contain in addition to the above-mentioned fillers so-called lightweight fillers, which are selected from hollow glass spheres, flue ash, hollow plastics spheres based on phenol resins, epoxy resins or polyesters, hollow ceramic spheres, or organic lightweight fillers of natural origin, such as ground nutshells, for example the shells of cashew nuts, coconuts or groundnut shells, as well as cork powder or coke powder. Particular preference is given to such lightweight fillers based on hollow glass or ceramic microspheres.

[0037] In another embodiment, the matrix materials for the thermosetting, thermally-expandable molded bodies additionally contain fibers based on aramide fibers, carbon fibers, glass fibers, polyamide fibers, polyethylene fibers or polyester fibers, those fibers preferably being pulp fibers or staple fibers having a fiber length of from 0.5 to 6 mm and a diameter of from 5 to 20 mm. Particular preference is given to polyamide fibers of the aramide fiber type, or to polyester fibers.

[0038] Although any suitable expanding agents may be employed, such as, e.g., azo compounds, hydrazides and the like, particular preference is given to the expandable or expanded hollow plastic microspheres based on polyvinylidene chloride copolymers; they are commercially available under the trademark names DUALITE and EXPANCEL from Pierce & Stevens and Casco Nobel, respectively.

[0039] The adhesive compositions according to the present invention may also contain other common adjuvants and additives, such as plasticisers, reactive diluents, flow auxiliaries, wetting agents, tackifiers, ageing inhibitors, stabilisers and/or coloring pigments. Depending on the requirements made of the adhesive application in respect of its processing properties, its flexibility, the required rigidifying action and the adhesive bond to the substrates, the relative proportions of the individual components may vary within comparatively wide limits. Typical ranges for the main components of the curable adhesive of the present invention are as follows: 1 (a) epoxy - based prepolymer from 10-70 wt. % (b) acrylate-terminated urethane from 1-15 wt. % (c) liquid epoxy resins from 10 to 50 wt. % (d) hardener and accelerator from 0.5 to 10 wt. % (e) expanding agent from 0 to 5 wt. % (f) lightweight filler from 0 to 50 wt. % (g) fillers from 3 to 30 wt. % (h) fibers from 0 to 5 wt. % (i) pigments from 0 to 1 wt. %

[0040] In the cured state, the following improvements are achieved as compared with the prior art:

[0041] higher impact resistance or toughness in expanded and unexpanded applications

[0042] improved flow characteristics at ambient temperatures which permit pumping to the worksite at temperatures well below cure temperatures

[0043] higher resistance to pressure

[0044] lower brittleness

[0045] improved resistance to cold and heat

[0046] reduced temperature dependence of the resistance to pressure from −30° C. to +90° C.

[0047] constant force level over the deformation path

[0048] reduction in density (specific weight)

[0049] low water absorption.

[0050] In the preparation of the epoxy prepolymer reaction product, the following compounds may be used as amino-terminated polyethylene glycols (ATPEG) or polypropylene glycols (ATPPG):

[0051] 1. linear amino-terminated polyethylene glycols (ATPEG) having the formula

H2N—(CH2)2—[O—(CH2)2—O—(CH2)2]n—NH2

[0052] in which n=17 to 27.

[0053] 2. linear amino-terminated polypropylene glycols (ATPPG) having the formula: 1

[0054] in which n is 5 to 100. They are obtainable under the trade name Jeffamine® of the D-series. 2 Jeffamine ® Type n approx. molecular weight D-400 5-6 400 D-2000 33 2000 D-4000 68 4000

[0055] 3. trifunctional compounds having the formula 2

[0056] in which A is 3

[0057] or a 4

[0058] group and x, y and z independently of each other are 1 to 40 and x+y+z are preferably >6. They are obtainable under the trade name Jeffamine® of the T-series. 3 Jeffamine ® Type A (initiator) approx. molecular weight T-403 trimethylol propane 440 T-3000 glycerin 3000 T-5000 glycerin 5000

[0059] Amino-terminated polyalkylene glycols containing both oxyethylene and oxypropylene repeating units may also be utilized.

[0060] As already mentioned, the properties of the curable adhesive can be controlled by varying the ratios of the resin components especially the ratio of the epoxy based prepolymer and the acylate terminated urethane resin according to the present invention. Referring to the epoxy based prepolymer in a preferred embodiment, 0.5 to 1 equivalent (30 to 50 wt-%) of epoxy resin a) which is solid at room temperature and 0.5 to 1 equivalent (10 to 25 wt-%) of epoxy resin b) which is liquid at room temperature are reacted with 0.125 to 0.5 equivalent (35 to 50 wt-%) of the amino-terminated polyethylene or polypropylene glycols, it being possible for 0.5 to 10 wt-% to be a trifunctional ATPPG. The heat-resistance of this cold-flexible resin component can be further improved by adding dimeric acid and/or butadiene-nitrile rubber/DGEBA or DGEBF adducts. More specifically, this reaction product can be modified by adding other modified epoxy resins such as:

[0061] i) adducts of dimeric fatty acids having varying molecular weights with epoxy resins of the diglycidyl ether type of bisphenol A or F (DGEBA or DGEBF) (e.g. Epikote® or EPON® 872); and/or

[0062] ii) adducts of carboxyl-terminated butadiene-nitrile rubber (CTBN) (Hycar® 1300X8, 1300X13;Struktol®) with DGEBA or DGEBF

[0063] When reacting the epoxy resins with the ATPEG/ATPPG, an excess of epoxy groups over the amino groups is used so that the latter react completely with epoxide groups. Typically, there is a 1.5 to 10-fold excess, for example a 3.5-fold excess of EEW over the active hydrogen equivalents (AHEW) of the amines.

[0064] In preparing the curable adhesive according to the present invention, the expoxy-based prepolymer resin component is initially prepared in a first stage. To this end, preferably, the solid epoxy resin a) and the liquid epoxy resin b) are reacted with the ETPEG or ATPPG c) in the desired ratio. The reaction takes place at high temperature, preferably at 90 to 130° C., for example at approximately 120° C., for a duration of e.g. three hours.

[0065] The resultant resin is generally solid or viscous at room temperature. It can be directly further processed by admixture with the acrylate terminated urethane resin and latent curing agent to obtain the curable adhesive according to this invention. However, it is also possible to prepare the resin in advance and to store it until further processing. For further processing, first of all it is necessary to heat the resin in order to lower its viscosity to such a degree that it can be mixed with the other constituents of the reactive hot melt adhesive. The resin is preferably heated to a temperature above 50° C., for example 60 to 110° C., particularly 70 to 95° C. Then the other modified resins including the acrylate terminated urethane resin are added and homogeneously mixed. It must be ensured that heating is not carried out to a temperature at which the added latent curing agent would be activated. For heating the resin and mixing with the other constituents of the reactive adhesive, a heated kneader or planetary mixer is suitably used. It is preferred to incorporate the latent curing agent in the mixture last after the other constituents. It is further preferred to cool the mixture, prior to adding the latent curing agent, to a temperature at the lower limit of the temperature range which is suitable for processing. In accordance with this invention, the epoxy-prepolymer mixture prepared as described above is mixed with an acrylate functional urethane resin and more preferably with acrylate terminated urethane such as those described in U.S. Pat. Nos. 3,297,745; 4,390,662; 4,719,268; 4,486,582 and 4,618,658, and 5,334,654, and 5,700,891 which are hereby incorporated by reference in their entirety. Acrylate-terminated urethane resins comprise the reaction product of an isocyanate terminated urethane prepolymer and an isocyanate reactive acrylate or methacrylate. Isocyanate terminated prepolymers are prepared by reacting a polyfunctional isocyanate, typically an aromatic diisocyanate, with a polyol, preferably a long chain polyether or polyester polyol, such as the ethylene and propyleneoxide adducts of C2 to C4 polyalcohols, polytetramethylene glycol (polyTHF), and polycaprolactone. For enhanced flexibilization of the polyepoxide resin, the molecular number average weight of the polyol should range from about 400 to 4000, preferably 700 to 2000. Flexibilizers utilizing a polyol having a number average molecular weight of less than 1000 generally lead to extremely viscous flexibilizers. Higher molecular weight polyols tend to cause premature phase separation in the formulated epoxy leading to poor physical properties. The preferred isocyanate-terminated urethane prepolymer is prepared by any known means, for example, a 2000 mw polypropylene glycol is reacted with an 80/20 2,4/2,6-toluenediisocyanate mixture. Any polyisocyanate such as methylenediphenyldiisocyanate (MDI), isophoronediisocyanate, (IPDI) or paraphenylenediisocyanate (PPDI) is also suitable.

[0066] The isocyanate-reactive acrylates and methacrylates typically used to prepare the acrylate terminated urethane prepolymers are hydroxy alkylacrylates and methacrylates and these include: hydroxyacrylates such as hydroxyethyl acrylate or methacrylate, hydroxypropyl acrylate or methacrylate, hydroxypentyl acrylate or methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl hexyl methacrylate, hydroxybutyl methacrylate and the like. Typically the ester portion of the acrylate or methacrylate is from a C2-C8 alcohol.

[0067] Additional materials which can be used to prepare substances which we choose to describe as included within the definition of acrylate terminated urethane resins include the following:

[0068] 1) prepolymers having number average molecular weights of 250-10,000, preferably 700-4000, and having glass transition temperatures below about 10 degrees C., preferably below about minus 10 degrees C. The average functionality of these prepolymers is at least 2, preferably 2 to 6 and particularly preferably 2 to 3. The terminal functional groups of the prepolymer may be amino or hydroxyl or carboxyl or mercapto, preferably, hydroxyl.

[0069] Particularly preferred prepolymers include linear and branched polypropylene glycols having number average molecular weights about 700 to about 4000;linear and branched polytetrahydrofurans having number average molecular weights between about 700 and about 4000;linear and branched poly(1,2-buyleneoxide) having number average molecular weights between about 700 and about 4000;and hydroxyterminated polyesters having number average molecular weights between about 700 and about 4000.

[0070] 2) polyisocyanates, preferably diisocyanates or triisocyanates such as isophonoronediisocyanate, methylenediphenyldiisocyanate, toluenediisocyanate, hexamethylenediisocyanate,tetramethylxylylenediisocyanate, and the like.

[0071] 3) isocyanate-reactive acrylates or methacylates, preferably hydroxyacrylates or—methacrylates such as hydroxyethylacrylate, hydroxypropylacrylate, hydroxyethylmethacrylate, hydroxypropylmethacylate, and the like.

[0072] Chain lengtheners such as diols and triols like 1,4 butanediol, 1,1,1 -trimethylolpropane, glycerol, 1,2,6-hexanetriol, pentaerythritol and the like optionally may be employed, preferably, from 0.01 to about 5% by weight.

[0073] Accordingly, one may react the NCO-reactive prepolymer with excess of polyisocyanate to yield an NCO-tipped prepolymer. When triol chain lengtheners, as described above, are added during this reaction and a suitable amount of polyisocyanate is used, branched NCO-tipped prepolymers are produced. Diol chain lengtheners can be used to control the molecular weight of the resulting prepolymer. This NCO-functional polymer is then reacted with the NCO-reactive acrylate or methacrylate to yield materials which are described for the purposes of this invention as (meth)acrylate terminated urethanes.

[0074] In another embodiment within the scope of this invention, the acrylate terminated urethane resins as described herein may also be employed as an adduct onto an epoxy resin.

[0075] It should be further understood that in yet another embodiment within the scope of the present invention, an acrylate terminated urethane resin is employed to produce a cureable adhesive composition without employing the amine-terminated glycol materials described above by admixing an epoxide resin having at least two 1,2-epoxide groups per molecule as described herein, a copolymer based on at least one 1,3-diene and at least one polar, ethyleneically unsaturated comonomer, such as acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, acrylic acid, or esters of acrylic or methacrylic acid with C1-C6 alcohols and a latent epoxide curing agent as described herein.

[0076] The reactive adhesive according to the invention is suitable for glueing or adhering parts made of different materials. It is preferably used for the glueing of metal parts and particularly for the glueing of steel sheets. These can also be electro-galvanized, hot-dip galvanized or zinc/nickel-coated steel sheets.

[0077] The adhesive is usually deposited in the form of a melt on one side, i.e. onto one of the two parts which are to be glued together. It is advantageous that the curable adhesive composition of this invention can be flowed or pumped to the work site at ambient temperatures or slightly above since, in most applications, it is preferable to ensure that the adhesive is heated only up to a temperature at which the latent curing agent is not yet activated. The two parts are joined together immediately after deposition of the adhesive mass and provisionally bonds the two parts to each other.

[0078] The resultant bond already has sufficient strength, e.g., so that the still uncured adhesive is not washed out if the metal sheets which are provisionally bonded to each other are treated for de-greasing purposes in a wash bath and then in a phosphating bath.

[0079] The adhesive is preferably finally cured in an oven at a temperature which lies clearly above the temperature at which the adhesive melt was applied to the parts to be bonded and at or above the temperature at which the hardener and/or accelerators are activated (i.e., become reactive towards the other components of the adhesive). Curing preferably takes place at a temperature above 150° C., for example at 170° C., for about 30 minutes.

EXAMPLE 1

Preparation of Epoxy Pre-Polymer SF 65

[0080] The reaction products of linear and trifunctional ATPPG with DGEBA can be prepared separately or in the mixture. Resins A to J were prepared from the following constituents, the formulation size being 1 kg in each case: 4 Preparation of modified epoxy resins (in equivalents) EEW AHEW A B C D E F G H J liquid 187 0.765 0.765 0.765 0.765 0.69 0.765 — 1.785 — DGEBA semisolid 255 — — — — — — 1.122 — 1.122 DGEBA solid 475 0.765 0.765 0.765 0.765 0.692 — — — — DGEBA solid 537 — — — — — 0.266 — — — DGEBA CTBN 325 0.17 0.17 0.17 0.17 — — 0.147 — — adduct CTBN 190* — — — — — 0.125 — — 0.125 adduct Dimeric 650 — — — — 0.34 — — — — acid adduct Linear 1000 0.44 0.43 0.44 0.43 0.43 — — — — ATPPG Linear 500 — — — — — 0.334 0.286 0.238 0.334 ATPPG trifunct. 500 0.08 0.023 — — 0.013 — — 0.048 — ATPPG trifunct. 75 — — 0.011 0.023 — — — — — ATPPG Viscosity at 36 37 28 33 34 17 6.3 0.59 7.8 80° C. [Pa · s] *5% CTBN, 95% DGEBA

[0081] Resin mixtures A to J were melted at approximately 80° C. and introduced first into the kneader with delivery screw. then the additional resin (CTBN adduct or dimeric acid adduct) was added and homogeneously mixed at 80° C.

[0082] Abbreviations used herein are defined as follows:

[0083] CTBN=carboxyl-terminated butadiene-nitrile rubber

[0084] ATPPG=amino-terminated polypropylene glycol

[0085] DGEBA=diglycidyl ether of bisphenol A

[0086] EEW=epoxide equivalent weight

[0087] AHEW=active hydrogen equivalent weight

[0088] TSS=tensile shearing strength

[0089] TPS=t-peel strength

[0090] SF-65 =the pre-polymer product resulting from the above procedure

EXAMPLE 2

Preparation of the Acrylate Terminated Urethane

[0091] The NCO-reactive prepolymers are mixed for 45 min at 90-100° C. and 0.1-2 mbar to remove water. The polyisocyanate is then added in one portion under nitrogen at 50° C. The reaction mixture is mixed under nitrogen at 70-80° C. to a constant NCO-value. Then the NCO-reactive acrylate is added together with a polymerization inhibitor. 0.01% DBTL is added after 1 hour at 80° C. and the mixing is continued for additional 2 h, then the epoxy resin is added. 5 Acrylate Terminated Urethane Resin A: Weight in Weight Chemical name Tradename Component grams percent of component of Company Capa 305 275 10.7 Polycaprolactone Solvay Interox Capa 220 672 26.2 Polycaprolactone Solvay Interox MDI 538 21.0 Methylenediphenyldii socyanate HPMA 310 12.1 Hydroxypropyl methacrylate Epon 828 769 30.0 DGEBA

[0092] 6 Acrylate Terminated Urethane Resin B: Weight in Weight Chemical name Tradename Component grams percent of component of Company PTHF 650 392 39.0 Polytetrahydrofuran MDI 225 22.4 Methylenediphenyldii socyanate HPMA 86 8.6 Hydroxypropyl methacrylate Epon 828 301 30.0 DGEBA

[0093] 7 Acrylate Terminated Urethane Resin C: Weight in Weight Chemical name Tradename Component grams percent of component of Company PTHF 650 398 40.0 Polytetrahydrofuran MDI 225 22.6 Methylenediphenyldii socyanate HEA 73 7.3 Hydroxyethyl acrylate Epon 828 298 30.0 DGEBA

[0094] 8 Acrylate Terminated Urethane Resin D: Weight in Weight Chemical name Tradename Component grams percent of component of Company Capa 305 110 11.0 Polycaprolactone Solvay Interox Capa 220 267 26.7 Polycaprolactone Solvay Interox MDI 217 21.7 Methylenediphenyldii socyanate HEA 106 10.6 Hydroxyethyl acrylate Epon 828 300 30.0 DGEBA

[0095] 9 Acrylate Terminated Urethane Resin E: Weight in Weight Chemical name Tradename Component grams percent of component of Company Dynacoll 612 61.2 Polyester Degussa 7250 MDI 59 5.9 Methylenediphenyldii socyanate HEA 29 2.9 Hydroxyethyl acrylate Epon 818 300 30.0 DGEBA

[0096] 10 Acrylate Terminated Urethane Resin F: Weight in Weight Chemical name Tradename Component grams percent of component of Company Dynacoll 589 58.9 Polyester Polyol Degussa 7360 MDI 75 7.5 Methylenediphenyldii socyanate HEA 36 3.6 Hydroxyethyl acrylate Epon 828 300 30.0 DGEBA

[0097] 11 Acrylate Terminated Urethane Resin G: Weight in Weight Chemical name Tradename Component grams percent of component of Company Pluriol 551 45.4 Polypropyleneglycol BASF P 900 MDI 225 18.5 Methylenediphenyldii socyanate HEA 73 6.0 Hydroxyethyl acrylate Epon 828 364 30.0 DGEBA

[0098] 12 Acrylate Terminated Urethane Resin H: Weight in Weight Chemical name Tradename Component grams percent of component of Company Pluriol 1225 56.3 Polypropylene BASF P 2000 glycol MDI 225 10.3 Methylenediphenyldii socyanate HEA 73 3.4 Hydroxyethyl acrylate Epon 828 653 30.0 DGEBA

[0099] 13 Acrylate Terminated Urethane Resin J: Weight in Weight Chemical name Tradename Component grams percent of component of Company Pluriol 551 46.8 polypropylene BASF P 900 glycol IPDI 200 17.0 isophorone diisocyanate HEA 73 6.2 Hydroxyethyl acrylate Epon 828 353 30.0 DGEBA

[0100] 14 Acrylate Terminated Urethane Resin K: Weight in Weight Chemical name Tradename Component grams percent of component of Company Pluriol 1225 57.2 polypropylene BASF P 2000 glycol IPDI 200 9.3 isophorone diisocyanate HEA 73 3.4 Hydroxyethyl acrylate Epon 828 642 30.0 DGEBA

[0101] 15 Acrylate Terminated Urethane Resin L: Weight in Weight Chemical name Tradename Component grams percent of component of Company Pluriol 551 49.8 polypropylene BASF P 900 glycol HDI 151 13.6 hexamethylene diisocyanate HEA 73 6.6 Hydroxyethyl acrylate Epon 828 332 30.0 DGEBA

[0102] 16 Acrylate Terminated Urethane Resin M: Weight in Weight Chemical name Tradename Component grams percent of component of Company Pluriol 425 54.8 polypropylene BASF P 2000 glycol Trimethylol 2.2 0.28 propane HDI 65 8.4 hexamethylene diisocyanate HEA 51 6.6 hydroxyethyl acrylate Epon 828 233 30.0 DGEBA

[0103] 17 Acrylate Terminated Urethane Resin N: Weight in Weight Chemical name Tradename Component grams percent of component of Company Ancarez 2364 1000 100.0 acrylate-functional Air Products urethane resin

EXAMPLE 3

Preparation of the Curable Adhesive

[0104] Curable adhesives are prepared by admixing SF-65 with an acrylate-terminated urethane resin and other components listed in Table 1 below with mixing for 45 minutes at a temperature controlled between 27-38 degrees C. (80-100 degrees F.) and pressure of 0.3-3 psi. 18 TABLE 1 all data in Grams Component/ Adhesive 1 2 3 4 5 6 7 8 9 10 11 12 SF-65 A 500 500 500 500 (Example 1) SF-65 B 500 (Example 1) SF-65 C 500 (Example 1) SF-65 D 500 (Example 1) SF-65 E 500 (Example 1) SF-65 F 500 (Example 1) SF-65 G 500 (Example 1) SF-65 H 500 (Example 1) SF-65 J 500 (Example 1) Polydis 3604 EPON 828 100 100 100 100 100 100 100 100 100 100 100 100 EPON 834 DER 351 100 100 100 100 100 100 100 100 100 100 100 100 DER 354 Resin A 100 (Example 2) Resin B 100 (Example 2) Resin C 100 (Example 2) Resin D (Example 2) Resin E (Example 2) Resin F (Example 2) Resin G (Example 2) Resin H (Example 2) Resin J 100 100 100 100 100 100 100 100 100 (Example 2) Resin K (Example 2) Resin L (Example 2) Resin M (Example 2) Resin N (Example 2) AMICURE 50 50 50 50 50 50 50 50 50 50 50 50 CG 1400 DE 83R 20 20 20 20 20 20 20 20 20 20 20 20 BUSAN 11-M1 10 10 10 10 10 10 10 10 10 10 10 10 Calcium 10 10 10 10 10 10 10 10 10 10 10 10 Oxide MONARCH 5 5 5 5 5 5 5 5 5 5 5 5 280 ULTRA 29 29 29 29 29 29 29 29 29 29 29 29 PFLEX DYHARD UR 6 6 6 6 6 6 6 6 6 6 6 6 300 EXPANCEL 10 10 10 10 10 10 10 10 10 10 10 10 551 Cab-O-Sil TS 720 30 30 30 30 30 30 30 30 30 30 30 30 EPODIL 749 30 30 30 30 30 30 30 30 30 30 30 30 Component/ Adhesive 13 14 15 16 17 18 19 20 21 22 23 24 SF-65 A 500 500 500 500 500 500 500 500 500 480 (Example 1) SF-65 B (Example 1) SF-65 C 480 (Example 1) SF-65 D (Example 1) SF-65 E (Example 1) SF-65 F (Example 1) SF-65 G (Example 1) SF-65 H 480 (Example 1) SF-65 J (Example 1) Polydis 3604 106 106 106 EPON 828 100 100 100 100 100 100 100 100 100 106 106 106 EPON 834 DER 351 100 100 100 100 100 100 100 100 100 DER 354 Resin A 89 (Example 2) Resin B (Example 2) Resin C (Example 2) Resin D 100 (Example 2) Resin E 100 (Example 2) Resin F 100 (Example 2) Resin G 100 (Example 2) Resin H 100 89 89 (Example 2) Resin J (Example 2) Resin K 100 (Example 2) Resin L 100 (Example 2) Resin M 100 (Example 2) Resin N 100 (Example 2) AMICURE 50 50 50 50 50 50 50 50 50 65 65 65 CG 1400 DE 83R 20 20 20 20 20 20 20 20 20 BUSAN 11-M1 10 10 10 10 10 10 10 10 10 37 37 37 Calcium Oxide 10 10 10 10 10 10 10 10 10 MONARCH 280 5 5 5 5 5 5 5 5 5 7 7 7 ULTRA PFLEX 29 29 29 29 29 29 29 29 29 300 300 300 DYHARD UR 300 6 6 6 6 6 6 6 6 6 7 7 7 EXPANCEL 551 10 10 10 10 10 10 10 10 10 8.4 8.4 8.4 Cab-O-Sil 30 30 30 30 30 30 30 30 30 41 41 41 TS 720 EPODIL 749 30 30 30 30 30 30 30 30 30 37 37 37 Component/ Adhesive 25 26 27 28 29 30 31 32 33 34 35 36 SF-65 A 778 (Example 1) SF-65 B 230 (Example 1) SF-65 C 480 480 (Example 1) SF-65 D 865 (Example 1) SF-65 E 500 500 (Example 1) SF-65 F 190 628 (Example 1) SF-65 G (Example 1) SF-65 H 480 480 (Example 1) SF-65 J 271 (Example 1) Polydis 3604 106 106 106 106 80 50 90 90 EPON 828 106 106 106 106 150 200 388 600 600 600 250 EPON 834 60 120 120 108 100 DER 351 60 300 DER 354 33 100 200 Resin A (Example 2) Resin B (Example 2) Resin C 89 89 (Example 2) Resin D (Example 2) Resin E (Example 2) Resin F (Example 2) Resin G 130 (Example 2) Resin H (Example 2) Resin J (Example 2) Resin K (Example 2) Resin L (Example 2) Resin M 89 89 200 130 280 (Example 2) Resin N 80 50 200 100 (Example 2) AMICURE 65 65 65 65 55 50 57 100 100 110 90 100 CG 1400 DE 83R 15 50 80 70 100 BUSAN 11-M1 37 37 37 37 20 20 10 25 25 20 15 20 Calcium Oxide 20 10 5 20 20 10 20 15 MONARCH 280 7 7 7 7 10 5 10 5 5 10 10 10 ULTRA PFLEX 300 300 300 300 180 300 80 213 213 127 146 158 DYHARD UR 300 7 7 7 7 6 10 4 10 10 20 16 16 EXPANCEL 551 8.4 8.4 8.4 8.4 8.8 9.5 7.8 13.4 13.4 18.8 19.1 17.8 Cab-O-Sil 41 41 41 41 30 32 34 64 64 66 65 62 TS 720 EPODIL 749 37 37 37 37 15 20 10 40 40 20 50 50 Component/ Adhesive 37 38 39 40 41 42 43 44 45 46 47 48 SF-65 A 778 (Example 1) SF-65 B 230 (Example 1) SF-65 C (Example 1) SF-65 D 865 (Example 1) SF-65 E 500 500 (Example 1) SF-65 F 190 314 (Example 1) SF-65 G (Example 1) SF-65 H 480 (Example 1) SF-65 J 271 (Example 1) Polydis 3604 225 300 380 106 80 50 90 90 EPON 828 615 800 800 106 150 200 388 600 600 300 250 EPON 834 60 120 120 54 100 DER 351 300 60 DER 354 135 33 50 200 Resin A (Example 2) Resin B (Example 2) Resin C 150 89 (Example 2) Resin D (Example 2) Resin E (Example 2) Resin F (Example 2) Resin G 130 (Example 2) Resin H (Example 2) Resin J (Example 2) Resin K (Example 2) Resin L (Example 2) Resin M 260 200 130 (Example 2) Resin N 280 380 80 50 200 50 (Example 2) AMICURE 100 106 128 140 65 55 50 57 100 100 55 90 CG 1400 DE 83R 100 60 100 15 50 40 70 BUSAN 11-M1 20 15 30 40 37 20 20 10 25 25 10 15 Calcium Oxide 15 15 10 20 10 5 20 20 29 20 MONARCH 280 10 8 10 10 7 10 5 10 5 5 5 10 ULTRA PFLEX 158 150 260 100 300 180 300 80 213 213 50 146 DYHARD UR 300 16 8 14 60 7 6 10 4 10 10 10 16 EXPANCEL 551 17.8 8.0 14.2 13.8 Cab-O-Sil 62 49 72 72 41 30 32 34 64 64 33 65 TS 720 EPODIL 749 50 37 15 20 10 40 40 50 Component/ Adhesive 49 50 51 52 SF-65 A (Example 1) SF-65 B (Example 1) SF-65 C (Example 1) SF-65 D 865 (Example 1) SF-65 E (Example 1) SF-65 F (Example 1) SF-65 G (Example 1) SF-65 H (Example 1) SF-65 J (Example 1) Polydis 3604 225 300 380 EPON 828 615 800 800 EPON 834 DER 351 300 DER 354 135 Resin A (Example 2) Resin B (Example 2) Resin C 150 (Example 2) Resin D (Example 2) Resin E (Example 2) Resin F (Example 2) Resin G (Example 2) Resin H (Example 2) Resin J (Example 2) Resin K (Example 2) Resin L (Example 2) Resin M 280 260 (Example 2) Resin N 380 (Example 2) AMICURE 100 106 128 140 CG 1400 DE 83R 100 60 100 BUSAN 11-M1 20 15 30 40 Calcium Oxide 15 15 10 MONARCH 280 10 8 10 10 ULTRA PFLEX 158 150 260 100 DYHARD UR 300 16 8 14 60 EXPANCEL 551 Cab-O-Sil 62 49 72 72 TS 720 EPODIL 749 50

[0105] 19 TABLE 2 Component Chemical name of component Tradename of Company SF-65 Polyoxyalkyleneamine epoxy adduct Polydis 3604 CTBN-Epoxy adduct Struktol EPON 828 diglycidylether of bisphenol A Resolution Performance Products EPON 834 diglycidylether of bisphenol A Resolution Performance Products DER 351 diglycidylether of bisphenol Dow A and F DER 354 diglycidylether of bisphenol F Dow Resin A-N acrylate functional urethane (Example 2) AMICURE CG Dicyandiamide Air Products 1400 DE 83R decabromodiphenyl ether Great Lakes Chemical Corp BUSAN 11-M1 Barium metaborate monohydrate Buckman Laboratories Calcium Oxide Calcium Oxide MONARCH 280 carbon black Cabot ULTRA PFLEX coated precipitated calcium Pfizer carbonate DYHARD UR 300 Fenuron SKW Trostberg EXPANCEL 551 Poly(acrylonitril-co-vinylidene Akzo Nobel chloride), isobutane Cab-O-Sil TS 720 treated fumed silica Cabot Epodil 749 Neopentyl glycol diglycidyl Air Products ether

[0106] Curing: Fix bond with clips and place specimens for 20 min in an air-circulating oven at160° C.

[0107] Table 3 below describes the properties of the above described adhesives following curing. 20 TABLE 3 PROPERTIES Viscosity Shear Strength T-Peel Strength (Flow at Expansion@ w/oil w/oil 80 psi, 160 C./ 160 C. for 160 C. for Adhesive # 0.104 inch) 20 min. 20 min. 20 min. 1 110 sec/20 gms @ AVE. = 97% EZG: AVE. = 13.8 MPa EZG: 32.1 C. 151 N/25 mm 25.8 sec/20 gms @ HDG: AVE. = 13.0 MPa HDG: 39.0 C. 133 N/25 mm 2 138 sec/20 gms @ AVE. = 89% EZG: AVE. = 9.1 MPa EZG: 33.3 C. 107 N/25 mm 31.4 sec/20 gms @ HDG: AVE. = 6.6 MPa HDG: 40.1 C. 94 N/25 mm 3 98.2 sec/20 gms @ AVE. = 99% EZG: AVE. = 13.6 MPa EZG: 32.4 C. 150 N/25 mm 20.8 sec/20 gms @ HDG: AVE. = 13.3 MPa HDG: 38.4 C. 138 N/25 mm 4 107 sec/20 gms @ AVE. = 90% EZG: AVE. = 11.4 MPa EZG: 32.0 C. 153 N/25 mm 23.8 sec/20 gms @ HDG: AVE. = 10.0 MPa HDG: 38.9 C. 129 N/25 mm 5 110 sec/20 gms @ AVE. = 103% EZG: AVE. = 12.5 MPa EZG: 31.8 147 N/25 mm 20.0 sec/20 gms @ HDG: AVE. = 12.1 MPa HDG: 39.5 C. 130 N/25 mm 6 59.9 sec/20 gms @ AVE. = 118% EZG: AVE. = 13.5 MPa EZG: 32.0 C. 139 N/25 mm 14.5 sec/20 gms @ HDG: AVE. = 12.1 MPa HDG: 39.3 C. 125 N/25 mm 7 23.7 sec/20 gms @ AVE. = 79% EZG: AVE. = 15.1 MPa EZG: 32.2 C. 126 N/25 mm 7.3 sec/20 gms @ HDG: AVE. = 14.2 MPa HDG: 39.5 C. 112 N/25 mm 8 10.1 sec/20 gms @ AVE. = 47% EZG: AVE. = 18.6 MPa EZG: 32.5 107 N/25 mm 5.9 sec/20 gms @ HDG: AVE. = 12.7 MPa HDG: 39.8 C. 87 N/25 mm 9 28.0 sec/20 gms @ AVE. = 81% EZG: AVE. = 15.6 MPa EZG: 32.0 C. 118 N/25 mm 9.4 sec/20 gms @ HDG: AVE. = 14.9 MPa HDG: 39.1 C. 102 N/25 mm 10 100 sec/20 gms @ AVE. = 99% EZG: AVE. = 14.4 MPa EZG: 32.2 C. 140 N/25 mm 23.7 sec/20 gms @ HDG: AVE. = 13.8 MPa HDG: 39.0 C. 123 N/25 mm 11 144 sec/20 gms @ AVE. = 106% EZG: AVE. = 11.9 MPa EZG: 30.9 C. 135 N/25 mm 26.1 sec/20 gms @ HDG: AVE. = 11.2 MPa HDG: 40.2 C. 122 N/25 mm 12 138 sec/20 gms @ AVE. = 96% EZG: AVE. = 14.1 MPa EZG: 31.5 C. 156 N/25 mm 25.8 sec/20 gms @ HDG: AVE. = 13.5 MPa HDG: 39.0 C. 144 N/25 mm 13 115 sec/20 gms @ AVE. = 99% EZG: AVE. = 13.8 MPa EZG: 31.9 C. 150 N/25 mm 29.8 sec/20 gms @ HDG: AVE. = 12.7 MPa HDG: 38.1 C. 135 N/25 mm 14 96.0 sec/20 gms @ AVE. = 87% EZG: AVE. = 8.1 MPa EZG: 31.3 C. 72 N/25 mm 20.8 sec/20 gms @ HDG: AVE. = 8.3 MPa HDG: 39.1 C. 72 N/25 mm 15 101.6 sec/20 gms @ AVE. = 92% EZG: AVE. = 4.5 MPa EZG: 31.5 C. 58 N/25 mm 23.0 sec/20 gms @ HDG: AVE. = 4.8 MPa HDG: 39.0 C. 53 N/25 mm 16 95.6 sec/20 gms @ AVE. = 101% EZG: AVE. = 16.8 MPa EZG: 32.3 C. 166 N/25 mm 25.8 sec/20 gms @ HDG: AVE. = 14.3 MPa HDG: 39.0 C. 131 N/25 mm 17 91.1 sec/20 gms @ AVE. = 108% EZG: AVE. = 14.6 MPa EZG: 32.3 C. 170 N/25 mm 25.4 sec/20 gms @ HDG: AVE. = 13.0 MPa HDG: 37.8 C. 143 N/25 mm 18 101 sec/20 gms @ AVE. = 92% EZG: AVE. = 13.0 MPa EZG: 32.2 C. 150 N/25 mm 25.4 sec/20 gms @ HDG: AVE. = 13.0 MPa HDG: 38.8 C. 139 N/25 mm 19 106 sec/20 gms @ AVE. = 95% EZG: AVE. = 13.5 MPa EZG: 32.3 C. 148 N/25 mm 28.1 sec/20 gms @ HDG: AVE. = 13.2 MPa HDG: 38.5 C. 135 N/25 mm 20 136 sec/20 gms @ AVE. = 109% EZG: AVE. = 15.2 MPa EZG: 32.4 C. 168 N/25 mm 36.8 sec/20 gms @ HDG: AVE. = 14.5 MPa HDG: 38.8 C. 157 N/25 mm 21 102 sec/20 gms @ AVE. = 97% EZG: AVE. = 13.8 MPa EZG: 32.4 C. 148 N/25 mm 22.0 sec/20 gms @ HDG: AVE. = 12.9 MPa HDG: 40.0 C. 135 N/25 mm 22 220 sec/20 gms @ AVE. = 112% EZG: AVE. = 16.9 MPa EZG: 32.4 C. 131 N/25 mm 40.1 sec/20 gms @ HDG: AVE. = 15.4 MPa HDG: 38.6 C. 133 N/25 mm 23 184 sec/20 gms @ AVE. = 116% EZG: AVE. = 15.7 MPa EZG: 32.3 C. 129 N/25 mm 31.8 sec/20 gms @ HDG: AVE. = 14.9 MPa HDG: 38.4 C. 124 N/25 mm 24 18.1 sec/20 gms @ AVE. = 116% EZG: AVE. = 17.6 MPa EZG: 32.3 118 N/25 mm 8.7 sec/20 gms @ HDG: AVE. = 14.3 MPa HDG: 39.8 C. 111 N/25 mm 25 198 sec/20 gms @ AVE. = 90% EZG: AVE. = 16.6 MPa EZG: 32.0 C. 125 N/25 mm 40.0 sec/20 gms @ HDG: AVE. = 15.3 MPa HDG: 38.3 C. 125 N/25 mm 26 14.3 sec/20 gms @ AVE. = 107% EZG: AVE. = 17.8 MPa EZG: 33.0 120 N/25 mm 8.8 sec/20 gms @ HDG: AVE. = 15.0 MPa HDG: 39.2 C. 122 N/25 mm 27 214 sec/20 gms @ AVE. = 92% EZG: AVE. = 15.4 MPa EZG: 32.5 C. 133 N/25 mm 40.8 sec/20 gms @ HDG: AVE. = 14.0 MPa HDG: 38. C. 127 N/25 mm 28 15.5 sec/20 gms @ AVE. = 102% EZG: AVE. = 17.0 MPa EZG: 32.6 109 N/25 mm 9.5 sec/20 gms @ HDG: AVE. = 14.6 MPa HDG: 38.8 C. 98 N/25 mm 29 71.8 sec/20 gms @ AVE. = 98% EZG: AVE. = 16.8 MPa EZG: 32.1 C. 129 N/25 mm 23.8 sec/20 gms @ HDG: AVE. = 15.6 MPa HDG: 39.2 C. 128 N/25 mm 30 67.6 sec/20 gms @ AVE. = 107% EZG: AVE. = 16.5 MPa EZG: 31.9 C. 130 N/25 mm 23.3 sec/20 gms @ HDG: AVE. = 15.5 MPa HDG: 39.0 C. 126 N/25 mm 31 82.4 sec/20 gms @ AVE. = 103% EZG: AVE. = 16.9 MPa EZG: 32.0 C. 125 N/25 mm 27.5 sec/20 gms @ HDG: AVE. = 15.7 MPa HDG: 39.2 C. 127 N/25 mm 32 70.5 sec/20 gms @ AVE. = 96% EZG: AVE. = 16.7 MPa EZG: 31.8 C. 132 N/25 mm 20.9 sec/20 gms @ HDG: AVE. = 15.5 MPa HDG: 39.2 C. 120 N/25 mm 33 90.2 sec/20 gms @ AVE. = 92% EZG: AVE. = 17.3 MPa EZG: 31.9 C. 138 N/25 mm 24.7 sec/20 gms @ HDG: AVE. = 15.9 MPa HDG: 39.1 C. 128 N/25 mm 34 74.4 sec/20 gms @ AVE. = 106% EZG: AVE. = 16.7 MPa EZG: 32.0 C. 130 N/25 mm 17.4 sec/20 gms @ HDG: AVE. = 15.2 MPa HDG: 39.3 C. 127 N/25 mm 35 76.1 sec/20 gms @ AVE. = 103% EZG: AVE. = 14.7 MPa EZG: 32.0 C. 150 N/25 mm 19.0 sec/20 gms @ HDG: AVE. = 14.3 MPa HDG: 39.4 C. 139 N/25 mm 36 71.0 sec/20 gms @ AVE. = 100% EZG: AVE. = 15.9 MPa EZG: 31.8 C. 132 N/25 mm 15.5 sec/20 gms @ HDG: AVE. = 14.8 MPa HDG: 39.3 C. 129 N/25 mm 37 65.9 sec/20 gms @ AVE. = 105% EZG: AVE. = 16.1 MPa EZG: 32.2 C. 130 N/25 mm 14.1 sec/20 gms @ HDG: AVE. = 15.5 MPa HDG: 39.0C 130 N/25 mm 38 14.2 sec/20 gms @ AVE. = 117% EZG: AVE. = 16.6 MPa EZG: 32.0 C. 100 N/25 mm 4.3 sec/20 gms @ HDG: AVE. = 15.5 MPa HDG: 39.1 C. 94 N/25 mm 39 16.2 sec/20 gms @ AVE. = 121% EZG: AVE. = 16.9 MPa EZG: 31.8 C. 113 N/25 mm 6.6 sec/20 gms @ HDG: AVE. = 15.4 MPa HDG: 39.0 C. 102 N/25 mm 40 12.9 sec/20 gms @ AVE. = 106% EZG: AVE. = 15.7 MPa EZG: 31.9 C. 130 N/25 mm 4.0 sec/20 gms @ HDG: AVE. = 15.0 MPa HDG: 38.7 C. 121 N/25 mm 41 16.1 sec/20 gms @ EZG: AVE. = 26.3 MPa EZG: 32.2 186 N/25 mm 9.1 sec/20 gms @ HDG: AVE. = 18.9 MPa HDG: 39.0 C. 164 N/25 mm 42 70.0 sec/20 gms @ EZG: AVE. = 27.0 MPa EZG: 32.3 C. 201 N/25 mm 23.5 sec/20 gms @ HDG: AVE. = 21.9 MPa HDG: 39.0 C. 172 N/25 mm 43 67.0 sec/20 gms @ EZG: AVE. = 26.9 MPa EZG: 32.09 C. 190 N/25 mm 24.7 sec/20 gms @ HDG: AVE. = 22.2 MPa HDG: 38.8 C. 166 N/25 mm 44 80.1 sec/20 gms @ EZG: AVE. = 27.1 MPa EZG: 32.0 C. 196 N/25 mm 31.9 sec/20 gms @ HDG: AVE. = 20.4 MPa HDG: 39.0 C. 167 N/25 mm 45 65.2 sec/20 gms @ EZG: AVE. = 25.7 MPa EZG: 31.9 C. 202 N/25 mm 19.7 sec/20 gms @ HDG: AVE. = 20.5 MPa HDG: 39.0 C. 160 N/25 mm 46 100.1 sec/20 gms @ EZG: AVE. = 26.6 MPa EZG: 31.8 C. 196 N/25 mm 28.1 sec/20 gms @ HDG: AVE. = 21.5 MPa 38.7 C. 47 150.0 sec/20 gms @ EZG: AVE. = 25.1 MPa EZG: 35.0 C. 191 N/25 mm 76.8 sec/20 gms @ HDG: AVE. = 19.4 MPa HDG: 39.2 C. 168 N/25 mm 48 42.6 sec/20 gms @ EZG: AVE. = 24.3 MPa EZG: 35.0 C. 203 N/25 mm 19.5 sec/20 gms @ HDG: AVE. = 19.0 MPa 39.2 C. 49 37.2 sec/20 gms @ EZG: AVE. = 24.7 MPa EZG: 35.1 C. 223 N/25 mm 15.5 sec/20 gms @ HDG: AVE. = 19.3 MPa 39.3 C. 50 9.0 sec/20 gms @ EZG: AVE. = 28.0 MPa EZG: 34.9 C. 167 N/25 mm 4.5 sec/20 gms @ HDG: AVE. = 20.9 MPa 39.0 C. 51 13.4 sec/20 gms @ EZG: AVE. = 27.6 MPa EZG: 35.1 C. 188 N/25 mm 6.2 sec/20 gms @ HDG: AVE. = 22.7 MPa 38.9 C. 52 10.0 sec/20 gms @ EZG: AVE. = 25.6 MPa EZG: 32.0 C. 214 N/25 mm 4.0 sec/20 gms @ HDG: AVE. = 21.8 MPa 38.7 C.

Claims

1. A curable adhesive which comprises:

A) a prepolymer reaction mixture of

(a) epoxy resin or resins prepared from bisphenol A or bisphenol F and epichlorohydrin having an epoxide equivalent weight of from about 150 to about 700;and

(b) an amino-terminated polyalkylene glycol, or a carboxyl terminated butadiene nitrile resin, or mixtures thereof;

B) an acrylate terminated urethane resin; and

C) a latent curing agent.

2. A curable adhesive of claim 1 which comprises an expanding agent to expand the adhesive during curing.

3. A curable adhesive of claim 2 wherein the expanding agent comprises expanded or expandable hollow plastic microspheres.

4. A curable adhesive of claim 1 in which the acrylate-terminated urethane resin comprises the reaction product of an isocyanate terminated urethane prepolymer and an isocyanate reactive acrylate or methacrylate.

5. A curable adhesive of claim 4 in which the isocyanate terminated prepolymer is prepared by reacting a polyfunctional isocyanate with a polyol.

6. A curable adhesive of claim 5 in which the polyfunctional isocyanate is an aromatic diisocyanate.

7. The curable adhesive of claim 5 in which the number average molecular weight of the polyol is from about 400 to about 4000.

8. The curable adhesive of claim 5 in which the number average molecular weight of the polyol is from about 700 to about 2000.

9. The curable adhesive of claim 4 in which the isocyanate terminated urethane prepolymer is prepared by reacting polypropylene glycol or polytetramethylene glycol and an isocyanate selected from the group consisting of 2,4 toluenediisocyanate, 2,6-toluenediisocyanate, 2,6 -toluenediisocyanate, 2,4 -toluenediisocyanate, methylenediphenyldiisocyanate, isophoronediisocyanate, hexamethylenediisocyanate, paraphenylenediisocyanate and mixtures thereof.

10. The curable adhesive of claim 4 in which the isocyanate reactive acrylates and methacrylates are selected from the group consisting of hydroxy alkylacrylates and hydroxyalkyl methacrylates.

11. The curable adhesive of claim 4 in which the isocyanate reactive acrylate or methacrylate is derived from a C2-C8 alcohol.

12. A curable adhesive composition comprising:a pre-reacted reaction product of

A) a pre-reacted reaction product of

(a) about 0.5 to about 1 equivalent of an epoxy resin which is solid at room temperature prepared from bisphenol A or bisphenol F and epichlorohydrin having an epoxide equivalent weight of from about 400 to about 700;

(b) about 0.5 to about 1 equivalent of an epoxy resin which is liquid at room temperature prepared from bisphenol A or bisphenol F and epichlorohydrin having an epoxide equivalent weight of from about 150 to about 220; and

(c) about 0.125 to about 0.5 equivalent of an amino-terminated polyalkylene glycol selected from the group consisting of polyethylene and polypropylene glycols; wherein said epoxy resins (a) and (b) are present in an amount such that a stoichiometric excess of at least 1 equivalent of epoxy groups over the amino groups is provided, said amino-terminated polyalkylene glycol comprising

i) a linear amino-terminated polyethylene glycol, or

ii) a linear amino-terminated polypropylene glycol, or,

iii) a linear amino-terminated polyethylene glycol and a trifunctional amino-terminated polypropylene glycol;

wherein about 4 to about 40% of the epoxy equivalents of the total epoxy resin component are replaced by an adduct of dimeric fatty acides on epoxy resins prepared from diglycidyl ethers of bisphenol A or F, or by an adduct of carboxyl-terminated butadiene-nitrile rubber on epoxy resins prepared from diglycidyl ethers of bisphenol A or F;

B) an acrylate terminated urethane resin which comprises the reaction product of an isocyanate terminated urethane prepolymer and an isocyanate reactive acrylate or methacrylate;

C) a latent curing agent; and

D) an expanding agent comprising hollow plastic microspheres.

13. A curable adhesive composition which comprises:

A) a reaction product of a polyepoxide resin having at least two 1,2-epoxy groups per molecule with polyoxy alkylene amine and, optionally, an adduct of carboxy terminated butadiene-nitrile rubber (BNR);

B) an acrylate terminated urethane resin; and

C) a latent curing agent.

14. A curable adhesive which comprises:

A) a prepolymer reaction mixture of

(a) an epoxy resin, an epoxy resin which is solid at room temperature prepared from bisphenol A or bisphenol F and epichlorohydrin having an epoxide equivalent weight of from about 400 to about 700;

(b) an epoxy resin which is liquid at room temperature prepared from bisphenol A or bisphenol F and epichlorohydrin having an epoxide equivalent weight of from about 150 to about 220; and

(c) an amino-terminated polyalkylene glycol selected from the group consisting of polyethylene and polypropylene glycols, or a carboxyl terminated butadienenitrile resin, or mixtures thereof;

B) an acrylate-terminated urethane resin;

C) a latent curing agent; and

D) an expanding agent comprising hollow microspheres.

15. A method of making a composite article which comprises: contacting a surface with a curable adhesive which comprises:

A) a prepolymer reaction mixture of

(a) epoxy resin or resins prepared from bisphenol A or bisphenol F and epichlorohydrin having an epoxide equivalent weight of from about 150 to about 700;

(b) an amino-terminated polyalkylene glycol selected from the group consisting of polyethylene and polypropylene glycols, or a carboxyl terminated butadiene nitrile resin, or mixtures thereof,

B) an acrylate-terminated urethane resin; and

C) a latent curing agent; and curing the adhesive in contact with the surface to prepare a composite article.

16. The method of claim 15 in which the surface is metal or plastic.

17. The method of claim 15 in which at least two surfaces are contacted with the curable adhesive and cured in contact therewith.

18. The method of claim 15 in which the curable adhesive is flowed into contact with the surface at a temperature between about 10 and about 50 degrees C.

19. The method of claim 15 in which the curable adhesive is flowed into contact with the surface at a temperature between about 20 and about 40 degrees C.

20. The method of claim 15 in which the curable adhesive contains hollow plastic microspheres.