DE10017783A1 - Thermosetting resin composition, especially useful as structural adhesive with high impact strength at low temperature, containing epoxy resin, reactive copolymer, acid anhydride reaction product and latent hardener - Google Patents

Abstract

A thermosetting resin composition (I) comprises: (A) epoxy resin having more than one epoxy group (on average) per molecule; (B) a copolymer having glass transition temperature -30 deg C or less and containing groups reactive with epoxy; (C) a reaction product containing on average more than one carboxy group per molecule; and (D) a latent hardener for (A). A thermosetting resin composition (I) comprises: (A) epoxy resin having more than one epoxy group (on average) per molecule; (B) a copolymer having glass transition temperature -30 deg C or less and containing groups reactive with epoxy (or a reaction product of such a copolymer with an excess of an epoxy resin as in (A)); (C) a reaction product containing on average more than one carboxy group per molecule, obtained from a triol or higher polyol or a tri- or polyfunctional amino-terminated polymer and a cyclic carboxylic acid anhydride; and (D) a latent hardener for (A), activated at elevated temperature. Independent claims are included for a method for hardening (I), by heating at 80-210 (preferably 120-180) deg C and for the uses of (I).

Description

The present invention relates to mixtures of special copolymers with at least a glass transition temperature of -30 ° C or lower and carboxyl-terminated polyamides or polyimides, mixtures of these compos nenten with epoxy resins and / or adducts of epoxy resins to the Co low glass transition temperature polymers and / or the polyamide or the polyimide and thermally activatable latent hardeners for the resin components, and if necessary accelerators, fillers, thixotropic Aids and other common additives. The invention further relates to a Processes for the preparation of these compositions and their use as a reactive adhesive.

Reactive hot melt adhesives based on epoxy are known. In machine, Vehicle or equipment construction, especially in aircraft construction, rail driving Witness construction or motor vehicle construction, the components from the different metallic components and / or composite materials in increasing Dimensions added with the help of adhesives. For structural bonds with ho hen requirements for strength are epoxy adhesive on a large scale substances used, especially as a thermosetting, one-component adhesive substances that are often formulated as reactive hot melt adhesives. Right Active hot melt adhesives are adhesives that are solid at room temperature  are and soften at temperatures up to about 80 to 90 ° C and how behave a thermoplastic material. Only at higher temperatures The latent ones present in these hot melt adhesives become about 100 ° C Thermally activated hardener, so that an irreversible hardening to a Du plastic is carried out. For joining the components, e.g. B. in the automotive industry, the adhesive first becomes warm on at least one substrate surface applied, the components to be connected are then joined. At the Ab cool then the adhesive solidifies and creates physical Solidify sufficient handling strength, i.e. H. a preliminary Connection. The components so interconnected are in the ver various washing, phosphating and immersion baths treated further. Only then is the adhesive applied in an oven at a higher temperature ren hardened.

Conventional adhesives and hot melt adhesives based on epoxy resin When hardened, zen are hard and brittle. That get with you Adhesives generally have a very high tensile shear strength on. With peeling, beating or peeling stress, especially at lower temperatures, however, these flake off, so that it with this type of stress the adhesive joint easily leads to loss of bond is coming. There have therefore been numerous proposals for epoxy resins Modified by flexible additives so that their brittleness clearly is reduced. A common method is based on the use of special ones Rubber adducts on epoxy resins, which act as a heterodisperse phase in the Epoxy resin matrix are embedded so that the epoxies become more impact-resistant, these epoxy resin compositions are also called "Toughened" designated. A common, known modification of epoxy resins the aforementioned type consists in the implementation of a polybutadiene co Acrylonitrile copolymer with caboxyl end groups with an epoxy resin.  

This rubber epoxy adduct is then subdivided into one or more dispersed in various epoxy resins. The reaction of the Epoxy resin with butadiene acrylonitrile chew containing carboxyl groups Tschuk be carried out so that there is no premature curing of the Adduct leads. Although such modified epoxy resin compositions a significant improvement in terms of their impact resistance compared to the unmodified epoxy resins is their behavior always against peeling or impact peeling loads not yet sufficient.

EP-A-0 343 676 discloses hot-melt adhesive compositions knows that from a mixture of several epoxy resins, a phenoli resin and a polyurethane epoxy adduct are composed. The polyurethane epoxy adduct contained therein consists of a conversion product of several polyalkylene glycol homo- and copolymers with primary and secondary OH groups, a diisocyanate and at least an epoxy resin. These hot melt adhesives are said to be together Opposition to different, commercial one-component Hot melt adhesive compositions in their shear strength, peel strength speed and impact resistance are improved via the adhesive properties the hardened adhesive joint at low temperatures does not cause anga ben made.

US-A-5 290 857 describes an epoxy resin adhesive composition containing an epoxy resin and a powdered core / shell polymer and a heat-activated hardener for the epoxy resin. The powdery Core / shell polymer is composed of a core containing one Acrylate or methacrylate polymer with a glass transition temperature of  -30 ° C or lower and a shell containing an acrylate or Methacrylate polymer containing crosslinking monomer units and des sen glass transition temperature is greater than or equal to 70 ° C, the Ge Weight ratio of the core to the shell in the range between 10: 1 to 1: 4 lies. These compositions are said to be excellent Adhesive properties such as impact strength, tensile shear strength and T- Have peel strength and also have good partial gelability Zen. Information on the properties of bonds with this adhesive fabrics at low temperatures are not made.

In an analogous manner, US-A-5 686 509 describes an adhesion enhancer kende composition for epoxy resins consisting of powdered Copolymer particles that are ionic with a mono- or divalent Metallka tion are networked. The core area of the core / shell polymer is made of a diene monomer and optionally crosslinking monomer units composed of a glass transition temperature less than or equal to -30 ° C. The shell copolymer has a glass transition temperature of at least 70 ° C and is made of acrylate or methacrylate monomer units and radically polymerizable unsaturated carboxylic acid units composed. The adhesive composition is said to be 100 parts Epoxy resin 15 to 60 parts by weight of the adhesion-enhancing copoly merpulvers and 3 to 30 parts by weight of a heat-activated curing have agent. These compositions are for use as Structural adhesives recommended for automotive parts. Information about the deep The temperature characteristics of such bonds are not made.

From EP-A-0 308 664 epoxy resin compositions are known which an epoxy adduct of a copolymer containing carboxyl groups of butadiene-acrylonitrile or similar butadiene copolymers contain so  like a reaction product of a soluble or disper in epoxy resin gizable elastomeric prepolymers with terminal isocyanate groups with a polyphenol or aminophenol and subsequent reaction this adduct with an epoxy resin. Furthermore, this together contain one or more epoxy resins. Furthermore for curing for these compositions, amino functional hardeners, Po lyarninoamides, polyphenols, polycarboxylic acids and their anhydrides or Catalytic hardening agents and, if necessary, accelerators gen. It is stated that these compositions as adhesive suitable materials that, depending on the specific composition, have high strength, high glass transition temperature, high peel strength, high impact strength or have high crack propagation resistance.

EP-A-0 353 190 describes epoxy resin composites in an analogous manner settlements containing an adduct of an epoxy resin and a carboxy gated butadiene-acrylonitrile copolymers and a reaction product of one hydroxyl-, mercapto- or amino-terminated polyalkylene glycol with one Phenol carboxylic acid with subsequent reaction of the phenolic group with an epoxy resin. EP-A-0 353 190 shows that these Compositions for the production of adhesives, adhesive films, Patches, sealants, varnishes or matrix resins are suitable.

EP-A-338985 describes modified epoxy resins which have a liquid Copolymer based on butadiene, a polar, ethylenic unsaturated comonomers and possibly other ethylenically unsaturated Comonomers contain and continue to be a reaction product dihydroxy-terminated or diamino-terminated polyalkylene glycols and Diisocyanates and a monophenol, a mercapto alcohol or an aliphatic lactam. According to the teaching of this document,  these compositions for the flexibilization of epoxy resins deploy. In addition to the aforementioned components, these are intended Compositions still epoxy resins and a hardener or Accelerator included. Such mixtures are said to be adhesives, Use adhesive films, patches, matrix resins, lacquers or sealants to let. Nothing is said about their behavior at low temperatures Information provided.

EP-A-366157 describes epoxy resins containing polyester Polyalkylene glycol base and hardener effective at higher temperatures. These compositions contain at least one compound with at least one 1,2-epoxy group in the molecule and one Reaction product of an aliphatic or cycloaliphatic diol with an aromatic hydroxycarboxylic acid and one with higher ones Temperature-effective hardener for the epoxy group-containing compound. The cured epoxy resin mixtures are said to be very should have good low-temperature flexibility and corrosion resistance. About their suitability as adhesives with high peel strength at low Temperatures, especially in the case of sudden loads, will not Statement made.

EP-A-272222 describes epoxy resins containing polyester Polyalkylene glycol base. These polyesters are derived from aliphatic, cycloaliphatic or aromatic carboxylic acids and / or aromatic Hydroxycarboxylic acids and aliphatic or cycloaliphatic diols, where at least 70% by weight of the carboxylic acid derivatives differ from dimer and / or derive trimer fatty acids. It is stated that such Epoxy resin compositions for the provision of thermosetting Adhesives are suitable for bonding steel and aluminum substrates  are. The hardened epoxy resin mixtures are said to be a good one Show low temperature flexibility and corrosion resistance.

From EP-A-307666 water-insoluble compounds are known which in are essentially free of isocyanate groups and at least two free ones have phenolic hydroxyl groups per molecule and which are available by reacting a prepolymeric polyisocyanate, which is an adduct a polyisocyanate to a prepolymeric polyhydroxy or Polysulfhydryl compound is or different from a prepolymer Derives polyetheramine. This prepolymeric polyisocyanate comes with at least one phenol with two or three phenolic hydroxyl groups or an aminophenol with one or two phenolic hydroxyl groups implemented. These compounds are then made with epoxy resins and thermally activatable hardeners added to be used as adhesives his. Information about the low temperature behavior, especially at abrupt load are not apparent from this document.

EP-A-381625 describes curable compositions containing a Epoxy resin, a hardener that can be activated at elevated temperature liquid copolymer based on butadiene, acrylonitrile and possibly others ethylenically unsaturated comonomers and a segmented Copolymer consisting essentially of recurring Soft segments with polypropylene glycol or polybutylene glycol units and selected hard segments with a softening temperature of above 25 ° C. According to the teaching of this document, the segmented Copolymers of polyether diols based on polypropylene glycol, Polytetramethylene glycol or amino terminated polyether diols and saturated aliphatic dicarboxylic acids with 4 to 12 carbon atoms or aromatic dicarboxylic acids with 8 to 12 carbon atoms  built up and can continue to be short chain diols or diamines in their Hard segment included. According to the teaching of this document, these are suitable Compositions as adhesives, in particular as hot melt adhesives as well as matrix resins or as surface coating agents. Strengths, in particular peel strengths with sudden load and low temperature are not revealed.

According to the teaching of EP-A-0 354 498 and EP-A-0 591 307, re active hot melt adhesive compositions from a resin component, at least one thermally activated latent hardener for the resin com component and optionally accelerators, fillers, thixotropic agents produce medium and other usual additives, the resin compo nente by the reaction of an epoxy solid at room temperature resin and an epoxy resin liquid at room temperature with one or several linear or branched polyoxypropylene with amino end group pen are available. The epoxy resins in such an amount, based on the amino-terminated polyoxypropylene, that an excess of epoxy groups based on the amino groups ge is guaranteed. These adhesive compositions already have one high peeling resistance in the angle peeling test, which also at low Temperatures are maintained.

The as yet unpublished DE-A-198 45 607.7 describes Condensation products from carboxylic acid dianhydrides, di- or Polyamines, especially polyoxyalkylene amines and polyphenols or Aminophenols and their suitability as structural components for epoxy resin Compositions. Such compositions contain additionally rubber-modified epoxy resins as well as liquid and / or solid Polyepoxides as well as usual latent hardeners and accelerators and possibly  Fillers. They are suitable as impact-resistant, impact-peeling and peeling-resistant Adhesives in vehicle construction. Although these adhesive compositions overall, a very good range of properties, even at low ones Temperatures, there is still a need for new and improved Adhesive compositions for these fields of application.

The object of the present invention is to provide reactive adhesives at the outset to improve the type mentioned in such a way that they are sufficient have sufficient flexibility, not only increased peel strength Room temperature but especially at low temperatures 0 ° C. In particular, the peel strength should be at low temperatures and sudden load have the highest possible value, thus structurally glued components even in the event of an accident (crash ver hold) correspond to the modern safety requirements in vehicle construction chen. In doing so, these improvements are intended without affecting the Peel strength and tensile shear strength achieved at high temperatures become. The reactive adhesives must also immediately after adequate application before the final curing have wash resistance. For this, the adhesive composition must be as a hot melt adhesive or as a highly viscous, hot-processable Be able to formulate adhesive. Another option is the wording as Adhesive, which is caused by a thermal pre-reaction in the so-called "body shell Furnace "or can be pre-gelled by induction heating of the parts to be joined.

The achievement of the object is the claims to men. It essentially consists in the provision of compositions that

• A) at least one epoxy resin with an average of more than one epoxy group per molecule  
• B) a copolymer with a glass transition temperature of -30 ° C or lower and epoxy reactive groups or a reaction product this copolymer with a stoichiometric excess of one Epoxy resin according to A),
• C) a reaction product can be produced from a trifunctional or polyfunctional polyol or a trifunctional or multifunctional amino-terminated polymer and one cyclic carboxylic acid anhydride, the reaction product on average more contains as a carboxyl group per molecule, and
• D) a latent component hardener that can be activated at elevated temperature A)

contain.

Components B) and C) can in a separate reaction with a large stoichiometric excess of epoxy resins of component A) are implemented and then, if necessary, with further epoxy resins, thermally activatable hardeners D) and / or other additives are mixed. It is however also possible components B) and C) without direct thermal Mix with the epoxy resin A) and then the latent Hardener D) and the other additives to mix.

Examples of the copolymers of structural component B) are 1,3-dienpo polymers with carboxyl groups and other polar ethylenically unsaturated Comonomers. Butadiene, isoprene or chloroprene can be used as diene butadiene is preferred. Examples of polar, ethylenically un saturated comonomers are acrylic acid, methacrylic acid, lower alkyl esters acrylic or methacrylic acid, for example its methyl or ethyl esters, amides of acrylic or methacrylic acid, fumaric acid, itaconic acid, Maleic acid or its lower alkyl ester or half ester, or maleic acid or itaconic anhydride, vinyl esters such as vinyl acetate or in particular acrylonitrile or methacrylonitrile. Especially before drawn copolymers A) are carboxyl-terminated butadienacrylonitrile copoly  mere (CTBN), which is in liquid form under the trade name Hycar from the B.F. Goodrich are offered. These have molecular weights between 2000 and 5000 and acrylonitrile levels between 10% and 30%. Specific examples are Hycar CTBN 1300 X 8, 1300 X 13 or 1300 X 15.

Furthermore, the structural components B) which are known from US Pat. No. 5,290 857 or core / shell polymers known from US Pat. No. 5,686,509 be set. The core monomers are said to have a glass transition temperature have a temperature of less than or equal to -30 ° C, these monomers are selected from the group of the aforementioned diene monomers or suitable acrylate or methacrylate monomers, if necessary the core poly contain small amounts of crosslinking comonomer units. The Shell is constructed from copolymers that are a glass transition system temperature of at least 60 ° C. The shell is preferably low ren alkyl acrylate or methacrylate monomer units (methyl or ethyl esters) and polar monomers such as (meth) acrylonitrile, (meth) acrylamide, sty role or radically polymerizable unsaturated carboxylic acids or Carboxylic anhydrides built up.

Another possibility for the structural component B) is the use of dendrimers, these are also called dentritic polymers, Cascade polymers or "starburst" polymers referred to. you will be as is known, step by step by linking two or more Monomers built up with each monomer already bound, so that with each step the number of monomer end groups increases exponentially and in the end a spherical tree structure is created. Such dendrime can e.g. B. by Michael addition of acrylic acid methyl ester to ammonia or amines can be produced.  

However, the adducts are particularly preferred for the structural component B) from epoxy resins and the aforementioned liquid CTBN rubbers.

The different variants of component C) can be represented by the following formulas I, IV and V and by structural elements II and III.

N is an integer between 3 and 6, m = two or three and X -O- or -NH-.  

R ¹ is an n-valent residue of a polyalkylene glycol after removal of the functional groups or a residue of a polybutadiene.

R ² is the remainder of a carboxylic acid anhydride and can be represented by structural elements II or III. In structure (II), R ³ and R ⁴ independently of one another preferably denote H or another covalent bond, but they can also be C1-C12-alkyl or aryl radicals. In the structural element (III), R ⁵ and R ^{6 can} independently be alkyl, hydrogen or aryl groups, but together they can also represent a cyclic carboxylic anhydride fused to the aromatic ring. Another possibility is that R ⁵ and R ⁵ together mean one or more fused rings on the aromatic ring represented in structural unit (III), e.g. B. in the naphthalene carboxylic acid derivatives.

The reaction products C) represented by formula (I) are obtained when a tri- or polyfunctional polyol or a tri- or polyfunctional amino-terminated polymer is reacted with a cyclic carboxylic anhydride of a dicarboxylic acid. Examples of such carboxylic anhydrides are maleic anhydride, succinic anhydride, phthalic anhydride. Structures of the formula (I) are also obtained when the tricarboxylic acids are reacted with trifunctional or polyfunctional polyols, but the radical R ² here carries two free carboxyl groups, ie one of the radicals R is in the structural elements (II) or (III) ³ to R ^{6 is} a carboxyl group.

In the particularly preferred reaction of trifunctional amino-terminated polyoxyalkylenes or polybutadienes (R ¹ ) with X = -NH- in formula (I) with tricarboxylic acid anhydrides or tetracarboxylic acid anhydrides, condensation products with the cyclic imide structures of the formulas (IV) or (V) are formed. If, for example, the anhydride of 1,2,3-propane tricarboxylic acid is used for the reaction, one of the two radicals R ⁷ and R ⁸ in structure (II) is a hydrogen atom and the second radical is -CH ₂ -COOH. When aromatic tricarboxylic acid anhydrides or tetracarboxylic acid anhydrides are used, imides having the structure (V) are formed, where the radicals R ⁹ and R ^{10 are} either independently an alkyl radical, hydrogen and at least one carboxylic acid radical (in the case of the tricarboxylic acid anhydrides). When using the tetracarboxylic anhydrides, R ⁹ and R ¹⁰ can either mean both carboxyl groups, they can also together form a cyclic acid anhydride ring or a further cyclic imide structure can be formed or an open-chain amide structure with an adjacent free carboxyl group. Here, by choosing the appropriate condensation conditions, the direction of synthesis can easily be influenced in the preferred direction. The parameters that can be selected are the stoichiometric ratio of amine to anhydride, reaction temperature and time. For the sake of completeness it should be mentioned that when the 1,8: 4,5-naphthalene-tetracarboxylic acid dianhydride is used, imide structures with a 6-membered imide ring are formed. In the formula (V), R ⁹ and R ^{10 can} furthermore mean fused aromatic rings, one of the aromatic rings additionally having at least one free carboxyl group. Furthermore, independently of one another, R ⁹ and R ^{10 can} mean aryl radicals having carboxylic acid groups or carboxylic anhydride groups which are either bonded directly to the aromatic ring shown in the formula (V) or via an alkyl group or a hetero atom.

Component C) is therefore a reaction product from a tri- or multifunctional polyol or a trifunctional or multifunctional amino-terminated Polymer and a cyclic carboxylic acid anhydride, the stoichiometric Ratio is chosen so that carbonic anhydrides of dicarboxylic acids there is an excess of the carboxylic acid anhydride component and the Condensation reaction is carried out so that it with the formation of the amide structures free carboxyl group according to formula (I) comes.

In principle, a large number of triamines or polyamines can be used for the condensation are used, but amino-terminated polyalkylene glycols are preferred, in particular the trifunctional amino-terminated polypropylene glycols,  Polyethylene glycols or copolymers of propylene glycol and ethylene glycol. This are also under the name "Jeffamine" (trade name of Huntsman) known. The trifunctional amino-terminated are also particularly suitable Polyoxytetramethylene glycols, also called poly-THF. Also are amino-terminated polybutadienes suitable as structural components, and Aminobenzoic acid esters of polypropylene glycols, polyethylene glycols or Poly-THF (known under the trade name "Versalink oligomeric Diamines") Air Products). The amino-terminated polyalkylene glycols or polybutadienes have molecular weights between 400 and 6000.

Instead of or together with the aforementioned polyamines, tri- or polyfunctional polyols can be used for the condensation reaction. In this case, in formula (I), X = -O-. Examples of the ones to be used Polyols are the OH-functional analogues of the aforementioned amino-terminated Links. So it is at least trifunctional Polypropylene glycols, polyethylene glycols or copolymers of propylene glycol and Ethylene glycol or poly-THF and hydroxy-functional polybutadienes with a functionality greater than two.

Specific examples of carboxylic anhydrides are Maleic acid, succinic acid, citric acid, 1,2,3-propane tricarboxylic acid, Aconitic, phthalic, 1,2,3- or 1,2,4-benzenetricarboxylic anhydride, Mellophanoic acid, pyromellitic acid, 1.8: 4.5 or 2.3: 6.7 naphthalene tetracarboxylic acid, perylene dianhydride, biphenyltetracarboxylic acid, Diphenylether tetracarboxylic acid, diphenylmethane tetracarboxylic acid, 2,2- Diphenylpropane tetracarboxylic acid, benzophenone tetracarboxylic acid dianhydride, Diphenylsulfonetetracarboxylic acid dianhydride or mixtures thereof.

In principle, in addition to the aforementioned carboxylic anhydrides maleinized oils and fats as anhydride components for production of the condensation product B) are used. Maleated oils and  Fats and low molecular weight polyenes are known to be Reaction or by free radical reaction of maleic anhydride with unsaturated compounds.

As epoxy resins for component A) or for the epoxy adduct formation or for mixing with components B) and / or C) are suitable a variety of polyepoxides containing at least 2 1,2-epoxy groups per Have a molecule. The epoxy equivalent of these polyepoxides can vary between 150 and 4000 vary. The polyepoxides can in principle be saturated, unsaturated, cyclic or acyclic, aliphatic, alicyclic, aromatic or heterocyclic polyepoxide compounds. Examples for suitable polyepoxides include the polyglycidyl ethers which are characterized by Reaction of epichlorohydrin or epibromohydrin with a polyphenol in Presence of alkali. Polyphenols suitable for this 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, 1,5- Hydroxynaphthalene.

Other polyepoxides suitable in principle are the polyglycidyl ethers from Po lyalcohols or diamines. These polyglycidyl ethers are derived from polyalko like ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol kol, 1,4-butylene glycol, triethylene glycol, 1,5-pentanediol, 1,6-hexanediol or Trimethylolpropane.

Other polyepoxides are polyglycidyl esters of polycarboxylic acids for example, reactions of glycidol or epichlorohydrin with aliphatic  or aromatic polycarboxylic acids such as oxalic acid, succinic acid, embers aric acid, terephthalic acid or dimer fatty acid.

Other epoxides are derived from the epoxidation products olefinically saturated cycloaliphatic compounds or of native oils and fet started.

The epoxy resins, which are characterized by reak tion of bisphenol A or bisphenol F and epichlorohydrin. there are usually mixtures of liquid and solid epoxy resins used, the liquid epoxy resins preferably based on the Bisphenols A and have a sufficiently low molecular weight sen. In particular for adduct formation with components B) and / or C) liquid epoxy resins are used at room temperature, which in the Typically have an epoxy equivalent weight of 150 to about 220, an epoxy equivalent weight range from 182 to is particularly preferred 192.

The hardness of the reactive adhesive when cooled, i.e. H. especially the after the application to the substrate to be joined, but before the Aus curing depends on the degree of condensation and thus molecular weight in particular Special component C) and the ratio of solid epoxy resin to liquid epoxy resin. The higher the degree of condensation (and thus the molecular weight) of the condensation product C) and the larger the The proportion of solid epoxy resin in the composition is the harder the cooled, semi-crystalline adhesive.

As thermally activatable or latent hardener D) for the epoxy resin Binder system from components A), B) and C) can guanidines,  substituted guanidines, substituted ureas, melamine resins, guanamine Derivatives, cyclic tertiary amines, aromatic amines and / or their Mixtures are used. The hardener can both be involved stoichiometrically in the hardening reaction, they can however, it can also be catalytically active. Examples of substituted guanidines are methylguanidine, dimethylguanidine, trimethylguanidine, Tetramethylguanidine, methylisobiguanidine, dimethylisobiguanidine, Tetramethylisobiguanidine, hexamethylisobiguanidine, Hepamethylisobiguanidine and especially cyanoguanidine (Dicy andiamid). Alkylated are representative of suitable guanamine derivatives Benzoguanamine resins, benzoguanamine resins or methoximethyl called ethoxymethylbenzoguanamine. For the one-component, heat-hard the hot melt adhesive is of course the selection criterion low solubility of these substances at room temperature in the resin system, so that solid, finely ground hardeners are preferred, especially dicyandiamide is suitable. This is a good storage stability of the together setting guaranteed.

In addition to or instead of the aforementioned hardeners Catalytically active substituted ureas are used. these are especially p-chlorophenyl-N, N-dimethylurea (monuron), 3- Phenyl-1,1-dimethylurea (fenuron) or 3,4-dichlorophenyl-N, N- dimethyl urea (diuron). In principle, can also be catalytically active tertiary acrylic or alkyl amines, such as, for example, benzyldimethylamine, Tris (dimethylamino) phenol, piperidine or piperidine derivatives who used However, these often have too high a solubility in the adhesive material system, so that here no usable storage stability of the one-component system is achieved. Furthermore, various, preferably fixed Imidazole derivatives can be used as catalytically active accelerators.  

Representative are 2-ethyl-2-methylimidazole, N-butylimidazole, benzimidazole and NC ₁ to C ₁₂ alkylimidazoles or N-arylimidazoles.

As a rule, the adhesives according to the invention further contain themselves well-known fillers such as the various ground or precipitated ones ten chalks, soot, calcium magnesium carbonates, heavy spar as well as esp special silicate fillers of the aluminum-magnesium-calcium type Silicates, e.g. B. wollastonite, chlorite.

Furthermore, the adhesive compositions according to the invention common other auxiliaries and additives such. B. plasticizer, reactive thinners, rheology aids, wetting agents, anti-aging agents, stabilizers contain catalysts and / or color pigments.

The adhesives according to the invention can on the one hand be used as one-component formulate permanent adhesives, both as highly viscous warm appli Adhesives that can be formulated can be formulated as well as thermally curing bare hot melt adhesives. These adhesives can also be used as a single component nentige pre-gellable adhesives are formulated, in the latter case the compositions contain either finely divided thermoplastic Powder such as B. polymethacrylates, polyvinyl butyral or other thermopla tical (co) polymers or the curing system is adjusted so that a two-stage curing process takes place, the gelation step only one partial curing of the adhesive and the final curing in Vehicle construction z. B. in one of the painting ovens, preferably in the KTL oven, takes place.

The adhesive compositions according to the invention can also be used as two-component epoxy adhesives are formulated, in which the at  the reaction components only shortly before application are mixed, the curing then at room temperature or moderate elevated temperature takes place. Can as a second reaction component here the known Re for two-component epoxy adhesives Action components can be used, for example di- or Polyamines, amino-terminated polyalkylene glycols (e.g. Jeffamine, amino Poly-THF) or polyaminoamides. Other reactive partners can mercap tofunctional prepolymers such as. B. the liquid thiokol polymers. Basically, the epoxy compositions according to the invention also with carboxylic anhydrides as the second reaction component in two-component adhesive formulations are cured.

In addition to the applications mentioned in the introduction, the fiction moderate adhesive compositions also as potting compounds in the elec tro- or electronics industry, as a die-attach adhesive in electronics for Gluing components to be used on printed circuit boards. Another one Possible uses of the compositions according to the invention are Ma trix materials for composite materials such as B. fiber reinforced composite materials.

Further preferred fields of application for the invention Adhesive compositions both in one-part thermosetting Form as well as in two-component form are their use as Structural foam, for example to form internal stiffeners from Cavities in vehicle construction, with the expanding structural foams stiffen the cavity structure of the vehicle or their Increase the degree of energy absorption. Furthermore, the Compositions for the production of so-called "stiffening pads"  or for stiffening coatings of thin-walled sheets or Plastic components, preferably used in vehicle construction.

For the application area "structural foam", the Compositions have expanding properties included for this the known blowing agents based on gas-releasing chemical blowing agents or based on expanded or expanding hollow microspheres, the expanded hollow microspheres both on the basis of polymers and also on the basis of inorganic materials such as glasses or ceramic materials can be built.

A very particularly preferred field of application of the invention However, adhesives are structural bonds in vehicle construction.

Depending on the requirements for the adhesive with regard to its processing properties, flexibility, impact peel strength or tensile strength, the proportions of the individual components can vary within relatively wide limits. Typical areas for the main components are:

• - Component A): 10-45 wt .-%, preferably 15-30 wt .-%, where this component from one or more liquid and / or solid Composed of epoxy resins and possibly also down can contain molecular epoxides as reactive diluents,
• Component B): 5-25% by weight, preferably 10-20% by weight
• Component C): 5-30% by weight, preferably 5-20% by weight
• Fillers: 10-40% by weight,
• - Hardener component D) (for thermally curable one-component systems): 1-10% by weight, preferably 3-8% by weight,  
• Accelerator: 0.01 to 3% by weight, preferably 0.1 to 0.8% by weight,
• - Rheology aids (thixotropic agents): 0.5-5% by weight.

The sum of the components is 100% complementary.

As already mentioned at the beginning, the demands on modern ones are increasing Structural adhesives in vehicle construction continue to increase as more and more construction elements of a load-bearing nature can be joined by adhesive processes. How already in the essay by G. Kötting and S. Singh, "Requirements for Adhesives for Structural Connections in Car Body Engineering ", Adhäsion 1988, Heft 9, pages 19 to 26, the adhesives have to be practical Fulfill various aspects of manufacturing, including automatable ver work in short cycle times, liability on oiled sheets, liability on different sheet types and compatibility with the process conditions painting line (resistance to washing and phosphating baths, hardenable during baking of the KTL primer, resistance ge compared to the subsequent painting and drying operations). About that In addition, modern structural adhesives also have to be cured meet increasing strength and deformation properties. This includes ren the high corrosion or bending stiffness of the structural components such as the deformability under mechanical stress of the bond. A The highest possible deformability of the components ensures a considerable Safety advantage in the case of a sudden load (crash behavior) in one Accident. This behavior can best be determined by determining the Determine impact work for hardened bonds, here are both at high temperatures up to + 90 ° C and especially at low temperatures temperatures down to -40 ° C sufficiently high values for the impact work or Impact peeling is desirable or necessary. In addition, it should the highest possible shear strength can be achieved. Both strengths on a variety of substrates, mainly oiled sheets,  such as B. body steel sheet, according to various methods ver galvanized sheet steel, sheets made of various aluminum alloys or Magnesium alloys as well as with organic coatings of the type "Bonazinc" or "Granocoat" coated in the coil coating process Steel sheets can be achieved. As shown in the examples below will meet the adhesive compositions of the invention these requirements surprisingly to a very high degree.

The following examples are intended to explain the invention in more detail. Both Compositions are all parts by weight if not stated otherwise.

Examples General production for component B)

Under a nitrogen atmosphere and stirring, a carboxy- terminated poly (butadiene-co-acrylonitrile) (Hycar CTBN 1300 X 13) with one about 10 molar excess of a liquid DGEBA epoxy resin 3 hours long implemented until the reaction was constant. (DGEBA = Diglycidyl ether of bisphenol A).

General production for the condensation product C)

1 mole of the carboxylic anhydride was in a stirrable and heatable Reaction kettle under nitrogen atmosphere at 100 ° C to 190 ° C with 0.2 to 0.5 mol of a trivalent amino-terminated polyalkylene glycol 0.5 to Reacted for 3 hours, whereby the polyamine was presented and was first heated to approx. 100 ° C. Possibly. becomes the reaction product with 2 to 4 times the mass of an epoxy resin and 0.2 to 0.5% by weight  Triphenylphosphine reacted for 1-2 hours at 100 ° C until constant the reaction.

General manufacture of the adhesive

In a kneader, the com components B) and C) as well as a liquid epoxy resin and a solid Epoxy resin (A) with the addition of fillers, hardeners, accelerators and Rheology aids mixed until homogeneous and then, if necessary, in bottled while still warm in the storage containers.

Examples 1-9

According to the general preparation for component C) Resins listed in Table 1 were prepared.

Table 1

According to the general preparation for component B), Hycar CTBN 1300 X 13 and a liquid DGEBA resin made a product with 40% butyl rubber and an epoxy equivalent weight of 900, Viscosity at 80 ° C 200 Pa.s.

As comparative examples according to the teaching of EP 0 381 625 the in Resins listed in Table 2 based on divalent polyethers manufactured:

Table 2

Examples 10-24

From components C) according to Examples 1 to 5, component B) and a liquid DGEBA resin (epoxy equivalent weight 189), (Component A).

Dicyandiamide as a hardener, accelerator and hydrophobic silica as a thixotropic agent, adhesive compositions according to the invention were produced in accordance with the general preparation of the adhesive. The compositions are summarized in Table 3.

DGEBA: DGEBA resin, epoxy equivalent weight 189
Silica: Cabosil TS 720

From the components according to Examples 6 to 9, component B) and a liquid DGEBA resin (epoxy equivalent weight 189, component A), dicyandiamide as hardener, accelerator and hydrophobic silica as thixotropic agents were used as comparative examples Adhesive compositions according to the teaching of EP 0 381 625 manufactured. The compositions are summarized in Table 4.  

Table 4

Silica: Cabosil TS 720

Table 5 compares the adhesive properties of the examples according to the invention and the adhesive properties of adhesives according to the prior art. Examples 21-24 are adhesives according to the teaching of EP 0 381 625, as listed in Table 2. The adhesive of Example 25 is Terokal 5051 from Henkel Teroson, this adhesive was produced on the basis of the teaching of EP-A-0 354 498. The adhesive of Example 26 is a commercially available product of the prior art. It is believed that this adhesive was made based on the teaching of EP-A-0 308 664.

From the technical adhesive properties listed in Table 5 the Advantage of the adhesive compositions according to the invention Example 10-20 clearly if this with the examples 21-26 according the prior art are compared. The examples according to the invention show very high impact peel strength according to ISO 11343 at high Stroke speeds. In particular, this is due to high Impact peeling work values at low temperatures of -20 ° C and -40 ° C clear. At the same time, these compositions also show high Temperatures of 90 ° C a high tensile shear strength according to DIN 53283 and are in both values of the composition according to the previous one Far superior to the state of the art.

Claims (13)

1. Containing thermally curable composition

• A) at least one epoxy resin with an average of more than one epoxy group per molecule
• B) a copolymer with a glass transition temperature of -30 ° C. or lower and groups which are reactive towards epoxides or a reaction product of this copolymer with a stoichiometric excess of an epoxy resin according to
• C) a reaction product which can be prepared from a tri- or polyfunctional polyol or a tri- or polyfunctional amino-terminated polymer and a cyclic carboxylic anhydride, the reaction product containing on average more than one carboxyl group per molecule,
• D) a latent hardener for component A) which can be activated at elevated temperature.

2. Compositions according to claim 1, characterized in that component B) is a copolymer based on butadiene. 3. Compositions according to claim 2, characterized in that component B) a copolymer containing carboxyl groups on the Base of butadiene-acrylonitrile, butadiene (meth) acrylic acid esters Butadiene-acrylonitrile-styrene copolymer, a butadiene (meth) acrylate Styrene copolymer or a dendrimer. 4. Composition according to claim 2, characterized in that the Component B) is a core-shell polymer whose core polymer is a Diene polymer or a (meth) acrylate polymer with one  Glass transition temperature of -30 ° C or lower and that optionally with 0.01 to 5 wt .-% of a di-olefinic comonomer can be cross-linked and its shell polymer one Has a glass transition temperature of 60 ° C or higher and that Monomers from the group alkyl (meth) acrylate, (meth) acrylonitrile, (Methyl) styrene and olefinically unsaturated carboxylic acids or Carboxylic anhydrides or mixtures thereof is built up. 5. Composition according to at least one of the preceding claims, characterized in that component C)

• a) a carboxylic acid anhydride selected from maleic acid, succinic acid, citric acid, 1,2,3-propane tricarboxylic acid, aconitic acid, phthalic acid, 1,2,3- or 1,2,4-benzene tricarboxylic acid anhydride, mellophanoic acid, pyromellitic acid , 1,8: 4,5- or 2,3: 6,7-naphthalene tetracarboxylic acid, perylene dianhydride, biphenyl tetracarboxylic acid, diphenyl ether tetracarboxylic acid, diphenyl methane tetracarboxylic acid, 2,2-diphenyl propane tetracarboxylic acid, benzene phenon tetracarboxylic acid dianhydride, diphenyl sulfonetetracarboxylic acid or mixtures of these dianhydride and
• b) a polyamine selected from polyethylene glycol, polypropylene glycol, polyoxytetramethylene or polybutadiene triamine and / or an at least trifunctional polyethylene glycol, polypropylene glycol, polyoxytetramethylene glycol or their copolymers or OH-functional polybutadiene, the reaction product being produced on average more than one carboxyl group per Contains molecule.

6. Composition according to claim 2 to 5, characterized in that component C) according to claim 5 in a liquid polyepoxide was solved. 7. Composition according to claim 1 to 5, characterized in that component C) according to claim 5 with a stoichiometric Excess of a polyepoxide was reacted. 8. The composition according to at least one of the preceding claims, characterized in that it is a compound as latent hardener D) from the group dicyandiamide, guanamine, guanidine, aminoguanidine, solid aromatic diamines and / or a hardening accelerator as well E) optionally plasticizers, reaction diluents, rheology Auxiliaries, fillers, wetting agents and / or anti-aging agents and / or contains stabilizers. 9. Process for curing the composition with components A), B), C), D) and optionally E) according to claim 8 by heating the composition at temperatures between 80 ° C and 210 ° C, preferably 120 ° C to 180 ° C. 10. Use of the compositions according to claim 8 as high-strength, impact-resistant structural adhesive in vehicle construction, aircraft construction or rail vehicle construction. 11. Use of the compositions according to claim 8 as Structural foam to form internal stiffeners in cavities Vehicle construction and for the production of stiffening coatings for thin-walled sheets or plastic components.   12. Use of the compositions according to claim 8 for Manufacture of composite materials as casting compounds in the electrical or electronics industry and as a die-attach adhesive at Manufacture of printed circuit boards in the electronics industry. 13. A method for bonding metallic and / or composite materials characterized by the following essential process steps

• - Applying the adhesive composition according to claim 8 to at least one of the substrate surfaces to be joined, optionally after prior cleaning and / or surface treatment
• - Mating components
• - optionally pre-gelling the adhesive composition
• - Hardening of the bond by heating the components to temperatures between 80 ° C and 210 ° C, preferably between 120 ° C and 180 ° C.