EP3497164A1 - Blocked polyurethane impact modifiers for improving the impact strength of low-temperature curing single-component epoxy adhesives - Google Patents

Abstract

The invention relates to an impact modifier which is an isocyanate-terminated polymer, the isocyanate groups of which are partially or completely blocked by reaction with a blocking agent, obtainable by A) reacting a) two or more polyols comprising a1) polytetramethylene ether glycol and a2) at least one hydroxy-terminated polybutadiene, wherein the total proportion of polytetramethylene ether glycol and hydroxy-terminated polybutadiene is at least 95 wt.-%, relative to the total weight of polyols, and b) at least one acyclic aliphatic or cycloaliphatic polyisocyanate in the presence of c) at least one catalyst while forming an isocyanate-terminated polymer, and B) reacting the isocyanate-terminated polymer obtained in step A) with d) at least one blocking agent selected from the group consisting of phenols, 2-benzoxazolinones and pyrazoles in the presence of e) at least one organic bismuth catalyst while forming the partially or completely blocked isocyanate-terminated polymer. The use of the impact modifier in epoxy resin adhesives results in good impact strength even at low curing temperatures.

Description

 Blocked polyurethane impact modifiers to improve the impact strength one-component low-temperature curing

 Epoxy adhesives Description

Technical area

The invention relates to blocked polyurethane-based impact modifiers for low-temperature curing one-component epoxy resin adhesives.

PRIOR ART Conventional epoxy adhesives are distinguished by high mechanical strength, in particular high tensile strength. In the case of sudden stress on the bond, however, conventional epoxy adhesives are generally too brittle and can therefore by far not meet the requirements, in particular the automotive industry, under crash conditions in which both high tensile and peel stresses occur. Inadequate in this regard are often particularly the strengths at high, but especially at low temperatures (for example, <-10 ° C).

Since these adhesives are structural adhesives in particular and therefore these adhesives bond structural parts, high strength and impact resistance of the adhesive are of utmost importance.

In order to improve the impact resistance of epoxy adhesives, so-called impact modifiers are added to them. An impact modifier, also referred to as Toughener, is one of the most important formulation ingredients in structural adhesives. It decisively influences important parameters such as impact strength, resistance to aging, adhesion, in fact all physical properties. There is already a wide range of impact modifiers for epoxy resins known. These are mainly liquid copolymers or preformed core-shell particles. One important type of impact modifier is blocked polyurethane toughener polymers as key components for crash resistant structural adhesives.

Epoxy resin adhesives cure under normal stoving conditions of ideally about 180 ° C. Blocked polyurethanes are used as impact modifiers in one-component epoxy resin adhesives for automobile body construction. In this case, the adhesive is baked or cured together with the applied to the parts to be bonded electrocoating. Due to the trend towards lower penetration temperatures for painting and modified vehicle concepts, such as e.g. Automotive body parts and mixed aluminum-steel bodies require one component epoxy adhesives with lower cure temperatures. However, the epoxy adhesives with the conventional toughening modifiers have a lower impact resistance at low curing temperatures (130 ° C., 140 ° C.) than the epoxy adhesives cured at standard temperatures (about 175 ° C.).

A particular challenge is now to provide an epoxy resin adhesive having sufficient impact resistance in terms of deep curing conditions.

Presentation of the invention

The object of the present invention was therefore to provide impact modifiers which overcome the above-described problems of the prior art. In particular, toughening modifiers for epoxy adhesives should be provided which have good impact strength even at low cure temperatures in the Ensure range from 120 ° C-150 ° C with a maximum curing time of 30 min. In particular, a good impact strength at low temperatures of below -10 ° C, for example -30 ° C, should be maintained. Furthermore, good mechanical properties of the adhesives containing the impact modifier according to the invention are to be achieved, for example with regard to modulus of elasticity, breaking and tensile strength, tensile shear strength, angular peel strength and, in particular impact peel strength. These improved mechanical properties should be maintained even at low temperatures (<-10 ° C). In addition, the epoxy adhesives should have a high storage stability.

It has surprisingly been found that specific blocked polyurethane-based impact modifiers, in the preparation of which an organic bismuth compound is used as catalyst for the reaction of the isocyanate groups with the blocking agent, can markedly increase the impact strength of the epoxy resin composition even at lower curing temperatures. In addition, with the use of the organic bismuth compound as catalyst, the blocking agent no longer has to be used in significant excess.

Accordingly, the invention relates to an impact modifier which is an isocyanate-terminated polymer whose isocyanate groups are partially or completely blocked by reaction with a blocking agent obtainable by

A) reaction of a) two or more polyols comprising a1) poly-tetramethylene ether glycol and a2) at least one hydroxy-terminated polybutadiene, the total amount of polytetramethylene ether glycol and hydroxy-terminated polybutadiene being at least 95% by weight, based on the total weight of the polyols, and b) at least one cycloaliphatic or acyclic aliphatic polyisocyanate in the presence of c) at least one catalyst to form an isocyanate-terminated polymer, and B) reacting the isocyanate-terminated polymer obtained in step A) with d) at least one blocking agent selected from the group consisting of phenols, 2-benzoxazolinones and pyrazoles in the presence of e) at least one organic bismuth catalyst to form the partially or fully blocked isocyanate - terminated polymer.

The impact modifiers according to the invention surprisingly show an improved impact strength, in particular low-temperature impact strength, in one-component epoxy resin adhesives which are cured at low temperature.

Overall, improved mechanical properties, such as modulus of elasticity, fracture and tensile strength, tensile shear strength, peel strength and, in particular impact peel strength are obtained, which are retained even at low temperatures (<-10 ° C). In addition, the epoxy adhesives mixed with the impact modifiers according to the invention have a high storage stability. The invention also relates to a process for the preparation of these impact modifiers, their use and epoxy resin formulations containing these impact modifiers. Preferred embodiments are given in the dependent claims.

Way to carry out the invention

Usually curing temperatures of about 175 ° C are used for one-component epoxy adhesives. Low-temperature-curing (low bake) one-component epoxy resin adhesives are understood in the following to be heat-curing epoxy resin adhesives which, at lower temperatures in the range from 120 to 150 ° C., have a curing time of up to 30 minutes can be cured. Curing at higher temperatures is also possible.

Under low temperature impact strength is the impact strength of a cured adhesive at a temperature of less than -10 ° C, in particular at -30 ° C understood.

The prefix poly in terms such as polyol or polyisocyanate means that the compound has two or more of the named groups. A polyol is thus a compound having two or more hydroxy groups. A polyisocyanate is a compound having two or more isocyanate groups. Accordingly, a diol or a diisocyanate is a compound having two hydroxy groups or two isocyanate groups. A hydroxy-terminated polymer is a polymer having hydroxyl groups as end groups. An isocyanate-terminated polymer is a polymer having isocyanate groups as end groups. In the polymer according to the invention, these isocyanate groups are partially or completely blocked. An organic metal compound is a metal compound having at least one organic ligand.

The impact modifier according to the invention is an isocyanate-terminated polymer whose isocyanate groups are partially or completely blocked by reaction with a blocking agent.

The isocyanate-terminated polymer is obtainable by reacting a) two or more polyols comprising a1) polytetramethylene ether glycol and a2) at least one hydroxy-terminated polybutadiene, wherein the total content of polytetramethylene ether glycol and hydroxy-terminated polybutadiene is at least 95% by weight, based on the Total weight of the polyols, and b) at least one acyclic aliphatic or cycloaliphatic Polyisocyanate in the presence of c) at least one catalyst to form an isocyanate-terminated polymer.

The reaction of polyols and polyisocyanates in general is a common reaction to form polyurethanes. The isocyanate-terminated polymer formed is thus in particular an isocyanate-terminated polyurethane polymer.

The two or more polyols for producing the isocyanate-terminated polymer include polytetramethylene ether glycol. One or more polytetramethylene ether glycols can be used. Polytetramethylene ether glycol is also referred to as polytetrahydrofuran or PTMEG. PTMEG may e.g. by polymerization of tetrahydrofuran, e.g. via acid catalysis. The polytetramethylene ether glycols are in particular diols.

Polytetramethyleneether glycols are commercially available, e.g. As the PolyTHF ^® - products from BASF as PolyTHF ^® 2000, PolyTHF ^® 2500 CO or CO PolyTHF ^® 3000, the Terathane ^® products from Invista BV or Polymeg® ^® products from LyondellBasell.

The OH functionality of the polytetramethylene ether glycol employed is preferably in the range of about 2, e.g. in the range of 1, 9 to 2,1. This is due to the cationic polymerization of the starting monomer tetrahydrofuran.

Polytetramethylene ether glycols with OH numbers between 170 mg / KOH g to 35 mg KOH / g, preferably in the range from 100 mg KOH / g to 40 mg KOH / g, and very particularly preferably 70 to 50 mg KOH / g, are advantageous. Unless stated otherwise, the OH number is determined titrimetrically in accordance with DIN 53240 in the present application. Here, the hydroxyl number is determined by acetylation with acetic anhydride and subsequent titration of the excess acetic anhydride with alcoholic potassium hydroxide solution. With knowledge of the difunctionality, the OH equivalent weights or the average molecular weight of the polytetramethylene ether glycol used can be determined from the hydroxyl numbers determined by titration.

Polytetramethylene ether glycols advantageously used in the present invention preferably have an average molecular weight in the range from 500 to 5000 g / mol, more preferably 1000 to 3000 g / mol and particularly preferably in the range from 1500 to 2500 g / mol, in particular about 2000 g / mol, up. The figures refer to the calculation of the molecular weight from the titrated hydroxyl numbers as given above assuming a functionality of 2 for PTMEG. This method of determination is also commonly used by the producers of these polymers.

The two or more polyols for preparing the isocyanate-terminated polymer further include at least one hydroxy-terminated polybutadiene. It is also possible to use mixtures of two or more hydroxy-terminated polybutadienes.

The hydroxy-terminated polybutadiene (s) for preparing the isocyanate-terminated polymer are, in particular, those prepared by radical polymerization of 1,3-butadiene using, for example, an azonitrile or hydrogen peroxide initiator and their hydrogenation products. Hydroxy-terminated polybutadiene are commercially available, such as the poly bd®- products from Cray Valley as poly bd® R45V, Polyvest ^® HT Evonik and Hypro ^® 2800X95HTB of Emerald Performance Materials LLC.

The hydroxy-terminated polybutadiene preferably has a number average molecular weight (Mn), for example determined by gel permeation chromatography (GPC) with THF as the eluent and calibration with 1,4-polybutadiene- Standards, of less than 15,000, preferably less than 5,000, wherein the Mn is preferably in the range of 2000 to 4000 g / mol. The OH functionality of the hydroxy-terminated polybutadiene is preferably in the range from 1.7 to 2.8, preferably from 2.4 to 2.8.

Further preferred are hydroxy-terminated polybutadienes having an acrylonitrile content of less than 15%, preferably less than 5%, more preferably less than 1%, most preferably less than 0.1%. Most preferred are hydroxy-terminated polybutadienes free of acrylonitrile. This is particularly advantageous for higher values in terms of modulus of elasticity, tensile strength, tensile shear strength and impact peel strength (especially at low temperatures and low curing temperature) and a lower viscosity and a higher storage stability. Based on the total weight of the polyols used to prepare the isocyanate-terminated polymer, the total amount of polytetra methylene ether glycol and hydroxy-terminated polybutadiene is at least 95% by weight and preferably at least 98% by weight. In a preferred embodiment, only polytetramethylene ether glycol and hydroxy-terminated polybutadiene are used as polyols. All characteristics relating to the impact modifier mentioned in this application explicitly apply correspondingly to reaction products in which only polytetramethylene ether glycol and hydroxy-terminated polybutadiene are used as polyols. In addition to polytetramethylene ether glycol and hydroxy-terminated polybutadiene, it is optionally possible to use at least one different polyol, in particular chain extenders such as preferably tetramethylene glycol (TMP) or a trifunctional polybutylene oxide-based polyether polyol such as DOW VORAPEL T5001, in small amounts of less than 5% by weight. %, preferably less than 2 wt .-%, based on the total weight of the polyols used, are added. The chain extender is preferably a polyol having a molecular weight Mn of not more than 1500 g / mol, more preferably not more than 1000 g / mol. In this way, the isocyanate-side chain extension can be combined with a polyol-side chain extension.

The weight ratio of a1) polytetramethylene ether glycol to a2) the at least one hydroxy-terminated polybutadiene (a1 / a2) is preferably in the range of 70/30 to 30/70, more preferably 60/40 to 40/60, and most preferably in the range of about 50/50.

One or more acyclic aliphatic or cycloaliphatic polyisocyanates may be used to prepare the isocyanate-terminated polymer. Aliphatic polyisocyanates include acyclic and cyclic aliphatic polyisocyanates. Cyclic aliphatic polyisocyanates are also referred to as cycloaliphatic polyisocyanates. Preferably, the polyisocyanate is a diisocyanate.

Preferred diisocyanates are acyclic aliphatic or cycloaliphatic diisocyanates, which are preferably monomeric diisocyanates or dimers thereof. Examples are 1,4-tetramethylene diisocyanate, 2-methylpentamethylene-1,5-diisocyanate, 1,6-hexamethylene diisocyanate (HDI), 2,2,4- and 2,4,4-trimethyl-1,6-hexa-methylene diisocyanate (cf. TMDI), 1, 10-decamethylene diisocyanate, 1, 12-dodecamethylene diisocyanate, lysine and lysine ester diisocyanate, cyclohexane-1, 3- and -1, 4-diisocyanate, 1-methyl-2,4- and -2,6- diisocyanatocyclohexane and any desired mixtures of these isomers (HTDI or H6TDI), 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (= isophorone diisocyanate or IPDI), perhydro-2,4'- and -4,4'- diphenylmethanediisocyanate (HMDI or H12MDI), 1,4-diisocyanato-2,2,6-trimethylcyclohexane (TMCDI), 1,3- and 1,4-bis- (isocyanatomethyl) -cyclohexane, m- and p-xylylene diisocyanate. isocyanate (m- and p-XDI), m- and p-tetramethyl-1, 3- and -1,4-xylylene diisocyanate (m- and p-TMXDI), bis (1-isocyanato-1-methylethyl) naphthalene, dimer and trimer fatty acid isocyanates such as 3,6-bis (9-isocyanatonyl) -4,5-di (1-heptenyl) cyclohexene (dimetyl diisocyanate) or the like R dimers thereof, as well as any mixtures of the aforementioned isocyanates. Particularly preferred are HDI and IPDI and their dimers. By varying the stoichiometry of the reactants and / or a stepped reaction of the reactants, the structure or chain length of the isocyanate-terminated polymers can be varied.

On the one hand, e.g. in a first stage, in which only a part of the polyisocyanates is used, OH-functional polymers with chains of different lengths are obtained by an excess of the OH groups relative to the NCO groups. Such chain-extended polyols contain urethane groups in the chain and can be further reacted in a second stage with residual polyisocyanates to form isocyanate-terminated polymers. On the other hand, by a deficiency of the OH groups based on the NCO groups NCO-functional polymers can be obtained with different lengths chains.

The isocyanate-terminated polymer formed in step A) preferably has on average 2 to 4 polyol units per polymer.

For the preparation of the isocyanate-terminated polymer, the proportions of polyol and polyisocyanates are, in particular, such that the isocyanate groups are present in a stoichiometric excess relative to the hydroxy groups, the molar ratio of isocyanate groups to hydroxy groups being e.g. greater than 1.3, preferably greater than 3 to 2, e.g. in the range of 3 to 1 to 3 to 2, preferably close to in the range of 2 to 1.

For the reaction of the two or more polyols and the at least one aliphatic polyisocyanate in step A), a catalyst is used. The catalyst accelerates the reaction of the isocyanates with the polyols. These are preferably organic metal compounds as catalysts, in particular organotin compounds, and mixtures thereof.

The catalyst expediently prefers the NCO: OH reaction with respect to the NCO: water reaction, which is the case, for example, with fatty acid salts of Tin (II) is the case. The catalyst should be distinguished by a high catalytic activity and selectivity with respect to the urethanization reaction, ie the reaction of alcoholic OH groups with isocyanate groups, and thus a rapid construction of a high-quality polyurethane polymer of polyfunctional alcohols (as little as possible disturbed by moisture). Polyols) and polyisocyanates. On the other hand, the catalyst should have a sufficient resistance to hydrolysis in order to remain under ordinary storage conditions, ie at room temperature or at slightly elevated temperatures, over several months in a residual water-containing polyol composition without a strong loss of activity. Furthermore, the catalyst should minimize the thermal stability of the cured polyurethane polymer as little as possible. In addition, the catalyst should be liquid at room temperature or at slightly elevated temperatures, or be readily soluble in the polyurethane starting materials or in plasticizers, so that it can be easily used in room-temperature curable, solvent-free systems. Ultimately, the catalyst should have the lowest possible toxicity.

As the catalyst for the reaction in step A), an organic tin compound is preferred. Examples are dibutyltin diacetate, dibutyltin dilauride, dibutyltin diacetylacetonate, dioctyltin dithioglycolate, dioctyltin laurate and particularly preferably dibutyltin dilaurate. Optionally, zirconium, tin, iron, vanadium or indium salts can also be used as the catalyst.

This at least one catalyst for the reaction in step A) is preferably present in an amount in the range of 0.5 wt .-% to 0.001 wt .-%, more preferably from 0.025 wt .-% to 0.005 wt .-%, based on the total mass of the blocked impact modifier.

In the impact modifier of the invention, the isocyanate groups of the isocyanate group-terminated polymer are partially or completely blocked by reaction with a blocking agent in step B), wherein preferably at least 80%, preferably at least 96%, of the isocyanate groups of the isocyanate-terminated polymer are blocked. In a particularly preferred embodiment, the isocyanate groups are substantially completely blocked, ie at least 99%. The one blocking agent may be one or more blocking agents.

The blocking of isocyanate groups by appropriate blocking agents capable of thermo-reversibly reacting with isocyanate groups is a common practice in the art and can be readily accomplished by those skilled in the art. The person skilled in the art knows a wide number of suitable blocking agents or blocking groups, e.g. from the review articles by Douglas A. Wiek in Progress in Organic Coatings 36 (1999), 148-172 and in Progress in Organic Coatings 41 (2001), 1 -83, to which reference is hereby made.

The at least one blocking agent is a compound having an isocyanate-reactive group. The blocking agent is in particular a proton-active compound, which is also referred to as H-acidic compound. The hydrogen of the blocking agent, which can react with an isocyanate group (acidic acid), is usually bound to an oxygen atom or a nitrogen atom. In this case, the blocking agent can react via the acidic hydrogen in a nucleophilic addition reaction with free isocyanate functionalities.

Compounds with SH-reactive protons such as dodecanethiol or 2-mercaptopyridine, compounds with CH ₂ -reactive protons such as ethylacetoacetate and guanidines such as tetramethylguanidine are unsuitable as blocking agents for the present invention.

The at least one blocking agent is selected from the group consisting of phenols, 2-benzoxazolinones and pyrazoles, wherein phenols are particularly preferred. However, ortho-substituted phenols are generally less suitable.

The pyrazoles can e.g. have the following structural formula

where n R ¹⁵ and R ^{16 are} each independently H, alkyl, eg, C 1 -C ₄ alkyl, aryl, or aralkyl.

The phenols may be monophenols or polyphenols such as bisphenols, for example phenols of the formula HO-R ¹ , where R ^{1 is} a mono- or polynuclear substituted or unsubstituted aromatic group which optionally has one or more further aromatic hydroxyl groups.

As substituent R ¹ O of phenols of the formula HO-R ¹ , preference is given to monophenols or polyphenols, in particular bisphenols, after removal of a phenolic hydrogen atom, in particular those of the following structural formulas

and The radical Y in this case represents a saturated or olefinically unsaturated hydrocarbon radical having 1 to 20 C atoms, in particular having 1 to 15 C atoms. As Y, in particular allyl, methyl, nonyl, dodecyl or an unsaturated C 1-6 alkyl radical having 1 to 3 double bonds are preferred.

Examples of suitable blocking agents are phenol, cresol, resorcinol, pyrocatechol, 3-pentadecenylphenol (casanol from cashew nut shell oil), nonylphenol, 3-methoxyphenol, 4-methoxyphenol, phenols reacted with styrene or dicyclopentadiene, bisphenol A, bisphenol F, 2 , 2'-diallyl-bisphenol-A, 2-benzooxazolinone and 3,5-dimethylpyrazole. The most preferred blocking agent is 4-methoxyphenol.

The amount of blocking agent used is preferably selected such that the equivalent ratio of the isocyanate groups of the isocyanate-terminated polymer to the isocyanate-reactive groups (H-acidic groups, for example OH or NH) of the blocking agent for step B) is in the region of 1, 5 to 0.7, more preferably from 1.2 to 0.8, and most preferably close to 1: 1.

The reaction of the isocyanate-terminated polymer obtained in step A) with the at least one blocking agent in step B) takes place in the presence of an organic bismuth catalyst. The catalyst accelerates the reaction of the blocking agent with isocyanate-reactive groups with the isocyanate groups.

One or more organic bismuth compounds may be used as the catalyst in step B), with Bi (III) compounds being preferred. The at least one organic bismuth compound includes or is more preferably bismuth (III) neodecanoate or bismuth (III) 2-ethylhexanoate. Most preferably, the organic bismuth compound is bismuth (III) neodecanoate. The amount of the catalytically active center, in particular bismuth (III), of the at least one organic bismuth catalyst used in step B) is preferably in the range from 0.5% by weight to 0.002% by weight, preferably from 0.1 wt .-% to 0.004 wt .-%, particularly preferably from 0.03 wt .-% to 0.005 wt .-%, based on the total mass of the blocked impact modifier.

The present invention further relates to a process for producing an impact modifier comprising

A) the reaction of a) two or more polyols comprising a1) tetramethylene ether glycol and a2) at least one hydroxy-terminated polybutadiene, wherein the total content of polytetramethylene ether glycol and hydroxy-terminated polybutadiene at least 95 wt .-%, based on the total weight of the polyols , and b) at least one acyclic or cycloaliphatic polyisocyanate in

Presence c) at least one catalyst to form an isocyanate-terminated polymer, and

B) the reaction of the isocyanate-terminated polymer obtained in step A) with d) at least one blocking agent selected from the group consisting of phenols, 2-benzoxazolinones and

Pyrazoles in the presence of e) at least one organic bismuth catalyst to form the partially or completely blocked isocyanate-terminated polymer. All above details of the impact modifier according to the invention naturally apply correspondingly to the process according to the invention and vice versa.

The reaction of polyols and polyisocyanates and the conditions suitable for this purpose are familiar to the person skilled in the art. For the preparation of the isocyanate-terminated polymer in step A), a mixture of the polyols and the polyisocyanates is reacted in the presence of the catalyst as described above. Optionally, a gradual addition of Starting components, for example, as already explained above, the one or more polyols may be reacted with a portion of polyisocyanate to first obtain a hydroxyl-terminated polymer, and then the remaining polyisocyanate are added to obtain the isocyanate-terminated polymer.

For the reaction in step A), a catalyst is added. Examples of suitable catalysts are as described above, e.g. organic metal compounds, such as organic tin compounds, preferably dibutyltin dilaurate (DBTL). Optionally, stabilizers, e.g. for PTMEG, e.g. Butylhydroxytoluene (BHT).

The reaction in step A) is conveniently carried out at elevated temperature, e.g. at a temperature of at least 60 ° C, preferably at least 80 ° C, in particular at a temperature in the range of 80 ° C to 100 ° C, preferably by about 90 ° C. The duration naturally depends strongly on the reaction conditions chosen and may be e.g. ranging from 15 minutes to 6 hours. The progress of the reaction can be readily controlled by analysis of the isocyanate content in the reaction mixture.

For the reaction in step B), as described above, at least one organic bismuth compound is added as catalyst, preferably bi (III) neodecanoate.

The blocking of the isocyanate groups with the blocking agent and the conditions suitable for it are also familiar to the person skilled in the art. The reaction in step B) is expediently carried out at elevated temperature, for example at a temperature of at least 90.degree. C., preferably at least 100.degree. C., in particular at a temperature in the range from 100 to 135.degree. C., preferably around 110.degree , The duration naturally depends strongly on the chosen reaction conditions and may, for example, be in the range of 15 minutes to 24 hours. The progress or termination of the reaction can without be further controlled by analysis of the isocyanate content in the reaction mixture.

The products obtained in step A) and step B) may be used as they are, that is, used. a workup is generally not required.

The impact modifier according to the invention is particularly suitable for use in a one-component (1 K) epoxy resin adhesive. As a result, the 1 K epoxy resin adhesive can also be cured at low temperature, with improved impact strength, in particular low-temperature impact strength, being achieved.

It is therefore in particular a low-temperature-curing (low bake) one-component epoxy resin adhesive. The 1K epoxy resin adhesive is particularly thermosetting and may be liquid, pasty or solid. The 1 K epoxy resin is preferably a structural or crash strength adhesive, for example, for the automotive industry, OEM products EP / PU Hybrid, structural foams from epoxy resin systems (such as Sika Reinforcer ^®) or repair applications.

The 1 K epoxy resin adhesive according to the invention comprises a) at least one epoxy resin, b) at least one curing agent for epoxy resins and c) the impact modifier according to the invention. The impact modifier according to the invention has already been described above. The proportion of the impact modifier of the invention in the 1K epoxy resin adhesive can vary widely, but is e.g. in a range from 5 to 60% by weight, preferably from 10 to 25% by weight, based on the total weight of the epoxy resin composition.

The epoxy resin contained in the epoxy resin adhesive can be any conventional epoxy resin used in this field. Epoxy resins are, for example, from the reaction of an epoxide compound such as epichloro hydrin with a polyfunctional aliphatic or aromatic alcohol, ie a diol, triol or polyol. One or more epoxy resins can be used. The epoxy resin is preferably an epoxy liquid resin and / or a solid epoxy resin.

As epoxy liquid resin or solid epoxy resin are preferably diglycidyl ethers, such as the form I (I)

(I) wherein R ^{4 is} a divalent aliphatic or mononuclear aromatic or a dinuclear aromatic radical.

Examples of diglycidyl ethers are in particular

Diglycidyl ethers of difunctional saturated or unsaturated, branched or unbranched, cyclic or open-chain C2-C30 alcohols, such as e.g. Ethylene glycol, butanediol, hexanediol, octanediol glycidyl ether, cyclohexane dimethanol diglycidyl ether, neopentyl glycol diglycidyl ether;

Diglycidyl ethers of difunctional, low to high molecular weight polyether polyols, e.g. Polyethylene glycol diglycidyl ether, polypropyleneglycol diglycidyl ether;

Diglycidyl ethers of difunctional diphenols and optionally triphenols, which are understood not only pure phenols, but optionally also substituted phenols. The type of substitution can be very diverse. In particular, this is understood to mean a substitution directly on the aromatic nucleus to which the phenolic OH group is bonded. Phenols are furthermore not only understood as mononuclear aromatics, but also as polynuclear or condensed aromatics or heteroaromatics which have the phenolic OH group directly on the aromatic or heteroaromatic compounds. As bisphenols and optionally triphenols, for example, 1, 4-dihydroxybenzene, 1, 3 are suitable Dihydroxybenzene, 1, 2-dihydroxybenzene, 1, 3-dihydroxytoluene, 3,5-dihydroxybenzoate, 2,2-bis (4-hydroxyphenyl) propane (= bisphenol-A), bis (4-hydroxyphenyl) methane (= bisphenol-F ), Bis (4-hydroxyphenyl) sulfone (= bisphenol-S), naphthororcinol, dihydroxynaphthalene, dihydroxyanthraquinone, dihydroxy-biphenyl, 3,3-bis (p-hydroxyphenyl) phthalide, 5,5-bis (4-hydroxyphenyl) hexahydro-4,7-methanoindane, phenolphthalein, fluorescein, 4,4 '- [bis (hydroxyphenyl) -1,3-phenylenebis- (1-methyl-ethylidene)] (= bisphenol-M), 4,4'- [Bis (hydroxyphenyl) -1,4-phenylene bis (1-methylethylidene)] (= bisphenol-P), 2,2'-diallyl-bisphenol-A, diphenols and dicresols prepared by reacting phenols or cresols with Diisopropylidenbenzol, phloroglucinol, bile acid esters, phenol or cresol novolaks with -OH functionality from 2.0 to 3.5 and all isomers of the aforementioned compounds.

Particularly preferred epoxy resins are liquid epoxy resins of the formula (A-1) and solid epoxy resins of the formula (A-II).

(Alles)

Here, the substituents R ', R ", R'" and R "" independently of one another are either H or CH3. Furthermore, the index r stands for a value of 0 to 1. Preferably, r stands for a value of less than 0.2. Furthermore, the index s stands for a value of> 1, in particular> 1.5, in particular from 2 to 12. Compounds of the formula (A-II) with an index s greater than 1 to 1.5 are referred to by the skilled person as semisolid epoxy resins. For the present invention, they are also considered as solid resins. However, preference is given to solid epoxy resins in the narrower sense, ie where the index s has a value of> 1.5.

Such solid epoxy resins are commercially available, for example, from Dow or Huntsman or Hexion. Commercially available liquid epoxy resins of formula (A-1) are e.g. available as Araldite® GY 250, Araldite® PY 304, Araldite® GY 282 (Huntsman, or Hexion) or D.E.R. ™ 331 or D.E.R. ™ 330 (Dow) or D.E.R. ™ 332 (Dow) or Epikote 828 (Hexion).

The diglycidyl ether of the formula (I) is preferably an epoxy liquid resin, in particular an epoxy liquid resin of the formula (A1), in particular a diglycidyl ether of bisphenol A (BADGE), of bisphenol F and of bisphenol A / F , Furthermore, epoxidized novolacs are also preferred epoxy resins.

The epoxy resin adhesive further contains a hardener for the epoxy resin. The hardener is in particular a hardener which is activated by elevated temperature. These hardeners are described as latent hardeners. As used herein, "elevated temperature" is generally understood as meaning, for example, a temperature above 100 ° C., generally above 110 ° C. or more preferably in the range from 120 to 150 ° C. Combinations of dicyandiamide as hardener and a latent co-hardener are suitable as thermally activatable hardener systems for the described low-temperature curing epoxy resin adhesives, with which curing in the range from 120 ° C. to 150 ° C. can be achieved. Such co-hardeners, often referred to as dicyandiamide accelerators, are well known to those skilled in the art and include latent amines and amine derivatives such as biguanides, epoxy-amine adducts, encapsulated amines or amine derivatives (ie, amines or amine derivatives incorporated in one Protective matrix), complexes of amines and boron trifluoride, organic acid dihydrazides or imidazole derivatives such as 2-ethyl-2-methylimidazole, 2-isopropylimidazole, 2-hydroxy-N- (2- (2- (2-hydroxyphenyl) -4,5-dihydroimidazole). 1-yl) ethyl) benzamide. Particularly preferred are tert. Amine derivatives such as 2,4,6-tris (dimethylaminomethyl) phenol or benzyldimethylamines which are incorporated in a matrix of polymeric phenols such as PVP (poly (p-vinylphenol) or novolak for latency.) One known example is 2,4,6 Tris ((dimethylaminomethyl) phenol in a poly (p-vinylphenol) matrix as described, for example, in US 4713432 and EP 0197892. Further particularly effective co-hardeners include the class of substituted ureas, such as 3-chloro-4 -methylphenylurea (chlorotoluron), or phenyldimethylureas, in particular p-chlorophenyl-N, N-dimethylurea (monuron), 3-phenyl-1, 1-dimethylurea (fenuron) or 3,4-dichlorophenyl-Ν, Ν-dimethylurea (diuron) ,

Advantageously, the total amount of the curing agent or the combination of hardener and co-curing agent for epoxy resins is 2 to 14 wt .-%, preferably 5 to 10 wt .-%, based on the weight of the total composition. As hardeners for epoxy resins, in an alternative embodiment, in particular e.g. Polyamine, polymercaptans, polyamidoamines, amino-functional polyamine / polyepoxide adducts as are well known to those skilled in the art as curing agents. The epoxy resin adhesive may optionally further comprise at least one additional optional impact modifier which is different from the impact modifier of the invention already described. The additional impact modifiers may be solid or liquid.

In one embodiment, this additional impact modifier is a liquid rubber which is a carboxyl or epoxide terminated acrylonitrile / butadiene copolymer or a derivative thereof. Such liquid rubbers are commercially available, for example, under the name Hypro® (formerly Hycar®) CTBN and CTBNX and ETBN from Emerald Performance Materials LLC. As derivatives are in particular epoxy-containing elastomer-modified prepolymers, as under the product line Polydis®, preferably from the product line Polydis® 36 .., by the company Struktol® (Schill + Seilacher Group, Germany) or under the product line Albipox® (Evonik Hanse GmbH , Germany) are commercially available. In a further embodiment, the impact modifier is a polyacrylate liquid rubber which is completely miscible with liquid epoxy resins and only separates into microdroplets on curing of the epoxy resin matrix. Such polyacrylate liquid rubbers are available, for example, under the designation 20208-XPA from Dow (formerly Rohm and Haas).

It is clear to the person skilled in the art that, of course, mixtures of liquid rubbers can also be used, in particular mixtures of carboxyl- or epoxide-terminated acrylonitrile / butadiene copolymers or derivatives thereof with epoxy-terminated polyurethane prepolymers.

In another embodiment, the additional impact modifier is a solid impact modifier which is a block copolymer. The block copolymer is obtained from an anionic or controlled radical polymerization of methacrylic acid ester with at least one further monomer having an olefinic double bond. Preferred monomers having an olefinic double bond are those in which the double bond is conjugated directly with a heteroatom or with at least one further double bond. In particular, monomers are suitable which are selected from the group comprising styrene, butadiene, acrylonitrile and vinyl acetate. Preference is given to acrylate-styrene-acrylic acid (ASA) copolymers, obtainable, for example, under the name GELOY® 1020 from GE Plastics. Particularly preferred block copolymers are block copolymers of methyl methacrylate, styrene and butadiene. Such block copolymers are available, for example, as triblock copolymers under the group name SBM from Arkema. In a further embodiment, the additional impact modifier is a core-shell polymer. Core-shell polymers consist of an elastic core polymer and a rigid shell polymer. Particularly suitable core-shell polymers consist of a core (core) of elastic acrylate or butadiene polymer which wraps around a rigid shell of a rigid thermoplastic polymer. This core-shell structure is formed either spontaneously by demixing a block copolymer or is predetermined by the polymerization as latex or suspension polymerization with subsequent grafting. Preferred core-shell polymers are so-called MBS polymers, which are commercially available under the trade names Clearstrength® from Arkema, Paraloid® from Dow (formerly Rohm and Haas) or F-351® from Zeon. Particularly preferred are core-shell polymer particles which are already present as a dried polymer latex. Examples of these are GENIOPERL® M23A from Wacker with polysiloxane core and acrylate shell, radiation-crosslinked rubber particles of the NEP series, manufactured by Eliokem, or Nanoprene® from Lanxess or Paraloid® EXL from Dow. Further comparable examples of core-shell polymers are offered under the name Albidur® by Evonik Hanse GmbH, Germany. Likewise suitable are nanoscale silicates in an epoxy matrix, such as those offered under the trade name Nanopox by Evonik Hanse GmbH, Germany. In a further embodiment, the additional impact modifier is a reaction product of a carboxylated solid nitrile rubber with excess epoxy resin.

It has been found that one or more additional impact modifiers are advantageously present in the epoxy resin adhesive. It has proven to be particularly advantageous for such a further impact modifier to be an impact modifier of the formula (II) containing epoxide groups.

(Ii) Here, R ^{7 is} a divalent radical of a carboxyl group-terminated butadiene / acrylonitrile copolymer (CTBN) after removal of the terminal carboxyl groups. The radical R ⁴ is as defined and described above for formula (I). In particular, R ^{7 is} a residue obtained by formal removal of the carboxyl groups of a carboxyl group-terminated butadiene / acrylonitrile copolymer CTBN commercially available under the name Hypro® CTBN from Emerald Performance Materials LLC. R ⁷ is preferably a bivalent radical of the formula (ΙΓ).

 (ΙΓ)

R here stands for a linear or branched alkylene radical having 1 to 6 C atoms, in particular 5 C atoms, which is optionally substituted by unsaturated groups. In a particularly noteworthy embodiment, the substituent R0 represents a radical of the formula (II-a).

(Il-a) Furthermore, the index q 'stands for a value between 40 and 100, in particular between 50 and 90. The designations b and c stand for the structural elements which originate from butadiene and a for the structural element which originates from acrylonitrile. The indices x, m ', and p' in turn represent values which describe the relationship of the structural elements a, b and c to one another. The index x stands for values from 0.05 to 0.3, the index m 'for values from 0.5 to 0.8, the index p for values from 0.1 to 0.2 with the proviso that the sum of x, m 'and p is equal to 1. It will be understood by those skilled in the art that the structure shown in formula (ΙΓ) is to be understood as a simplified illustration. Thus, the blocks a, b and c may each be arranged randomly, alternately or block by block to each other. In particular, therefore, formula (ΙΓ) is not necessarily a triblock copolymer.

The impact modifier of the formula (II) is prepared by reacting a carboxyl-terminated butadiene / acrylonitrile copolymer (CTBN), in particular of the formula (III), where the substituents are as defined in formula (II), with a diglycidyl ether explained above of the formula (I) in a stoichiometric excess of the diglycidyl ether, ie that the ratio of the glycidyl ether groups to the COOH groups is greater than or equal to 2.

The proportion of the additional impact modifier (s) described above other than the epoxy-terminated impact modifier in the liquid rubber of the invention is, for example, zero to 45% by weight, preferably 1 to 45% by weight, in particular 3 to 35% by weight, based on the weight of the total composition.

The epoxy adhesive may, of course, include other ingredients. In particular, these are fillers, reactive diluents, such as epoxy-bearing reactive diluents, catalysts, stabilizers, especially heat and / or light stabilizers, thixotropic agents, plasticizers, solvents, mineral or organic fillers, blowing agents, dyes and pigments, corrosion inhibitors, surfactants, defoamers and adhesion promoters. For these additives, all known in the art can be used in the usual amounts.

The fillers are e.g. preferably mica, talc, kaolin, wollastonite, feldspar, syenite, chlorite, bentonite, montmorillonite, calcium carbonate (precipitated or ground), dolomite, quartz, silicas (pyrogenic or precipitated), cristobalite, calcium oxide, aluminum hydroxide, magnesium oxide, ceramic hollow spheres, Glass hollow spheres, organic hollow spheres, glass spheres, color pigments. Filler means both the organic coated and the uncoated commercially available and known in the art forms.

In a further embodiment, layer minerals, in particular layered minerals exchanged with organic ions, are used as fillers. The ion-exchanged layered mineral may be either a cation-exchanged or an anion-exchanged layered mineral. It is also possible that the adhesive simultaneously contains a cation-exchanged layered mineral and an anion-exchanged layered mineral.

The cation-exchanged layered mineral is thereby obtained from a layered mineral in which at least part of the cations have been replaced by organic cations. Examples of such cation-exchanged layered minerals are, in particular, those mentioned in US Pat. No. 5,707,439 or in US Pat. No. 6,197,849. There is also the process for producing this cation-exchanged layer minerals. Preferred as a layer mineral is a layered silicate. The layer mineral is particularly preferably a phyllosilicate, as described in US Pat. No. 6,198,849, column 2, line 38, to column 3, line 5, in particular a bentonite. Layer minerals such as kaolinite or a montmorillonite or a hectorite or a lllit have proven to be particularly suitable.

At least part of the cations of the layered mineral are replaced by organic cations. Examples of such cations are n-octylammonium, trimethyldodecylammonium, dimethyldodecylammonium or bis (hydroxyethyl) octadecylammonium or similar derivatives of amines which can be obtained from natural fats and oils; or guanidinium cations or amidinium cations, or cations of the N-substituted derivatives of pyrrolidine, piperidine, piperazine, morpholine, thiomorpholine; or cations of 1,4-diazabicyclo [2.2.2] octane (DABCO) and 1-azabicyclo [2.2.2] octane; or cations of N-substituted derivatives of pyridine, pyrrole, imidazole, oxazole, pyrimidine, quinoline, isoquinoline, pyrazine, indole, benzimidazole, benzoxazole, thiazole phenazine and 2,2'-bipyridine. Also suitable are cyclic amidinium cations, especially those disclosed in US Pat. No. 6,198,849 at column 3, line 6 to column 4, line 67.

Preferred cation-exchanged layer minerals are known to the person skilled in the art under the name Organoclay or Nanoclay and are commercially available, for example, under the group names Tixogel® (Byk Additives & Instruments) or Nanofil® (Byk Additives & Instruments), Cloisite® (or Nanomer® (Nanocor Inc.) or Garamite® (Byk Additives & Instruments).

The anion-exchanged layered mineral is obtained from a layered mineral in which at least part of the anions have been exchanged for organic anions. An example of an anion-exchanged layered mineral is a hydrotalcite in which at least part of the carbonate anions of the intermediate layers have been replaced by organic anions. Advantageously, the total amount of the total filler is 3 to 50 wt .-%, preferably 5 to 35 wt .-%, in particular 5 to 25 wt .-%, based on the weight of the total composition.

The reactive diluents are in particular:

Glycidyl ethers of monofunctional saturated or unsaturated, branched or unbranched, cyclic or open-chain C ₄ -C 30 alcohols, in particular selected from the group consisting of butanol glycidyl ether, hexanol glycidyl ether, 2-ethylhexanol glycidyl ether, allyl glycidyl ether, tetrahydrofurfuryl and furfuryl glycidyl ether, trimethoxysilyl glycidyl ether.

 - Glycidyl ether of difunctional saturated or unsaturated, branched or unbranched, cyclic or open-chain C2-C3o alcohols, in particular selected from the group consisting of ethylene glycol, butanediol, hexanediol, Octandiolgylcidylether, Cyclohexandimethanoldigly- cidylether and Neopentylglycoldiglycidylether.

 Glycidyl ethers of trifunctional or polyfunctional, saturated or unsaturated, branched or unbranched, cyclic or open-chain alcohols, such as epoxidized castor oil, epoxidized trimethylolpropane, epoxidized pentaerythrol or polyglycidyl ethers of aliphatic polyols, such as sorbitol, glycerol or trimethylolpropane.

 Glycidyl ethers of phenolic and aniline compounds, in particular selected from the group consisting of phenylglycidyl ether, cresyl glycidyl ether, p-tert-butylphenyl glycidyl ether, nonylphenol glycidyl ether, 3-n-pentadecenylglycidyl ether (from cashew nut shell oil), N, N Diglycidylaniline and triglycidyl of p-aminophenol.

 - Epoxidized amines such as N, N-diglycidylcyclohexylamine.

Epoxidized mono- or dicarboxylic acids, in particular selected from the group consisting of glycidyl neodecanoate, glycidyl methacrylate, glycidyl benzoate, diglycidyl phthalate, tetra- and hexahydrophthalate, and diglycidyl esters of dimeric fatty acids and cetyl terephthalic and trimelitic esters. - Epoxidized di- or trifunctional, low to high molecular weight polyether polyols, in particular Polyethylenglycoldiglycidylether or Polypropylenglyco- diglycidylether. Particularly preferred are hexanediol diglycidyl ethers, cresyl glycidyl ethers, p-tert-butylphenyl glycidyl ethers, polypropylene glycol diglycidyl ethers and polyethylene glycol diglycidyl ethers.

Advantageously, the total proportion of the reactive diluent is from 0.1 to 20% by weight, preferably from 1 to 8% by weight, based on the weight of the total epoxy resin adhesive.

Suitable plasticizers are e.g. Phenolalkylsulfonsäureester or benzenesulfonic acid N-butylamide, which are available as Mesamoll® or Dellatol BBS from Bayer. Suitable stabilizers are e.g. optionally substituted phenols, such as butylhydroxytoluene (BHT) or Wingstay® T (elikem), sterically hindered amines or N-oxyl compounds such as TEMPO (Evonik).

In a particular embodiment, the epoxy resin adhesive further contains at least one physical or chemical blowing agent, in particular in an amount of 0.1 to 3 wt .-%, based on the weight of the adhesive. Preferred blowing agents are chemical blowing agents which release a gas on heating, in particular to a temperature of 100 to 200 ° C. It may be exothermic blowing agents, such as azo compounds, hydrazine derivatives, semicarbazides or tetrazoles. Preference is given to azodicarboxamide and oxy-bis (benzenesulfonylhydrazide), which release energy upon decomposition. Also suitable are endothermic blowing agents, such as sodium bicarbonate / citric acid mixtures. Such chemical blowing agents are available, for example, under the name Celogen® from Chemtura. Also suitable are physical blowing agents sold under the trade name Expancel® by Akzo Nobel. Expancel® and Celogen® are particularly preferred. By way of example, Table 1 lists components and proportions for a preferred 1K epoxy resin adhesive containing the impact modifier of the invention. Table 1 :

The curing of the epoxy resin adhesive according to the invention is carried out in particular by heating to a temperature which is above the heat activation of the thermally activated curing agent. This curing temperature is preferably a temperature in the range of 110 ° C to 220 ° C, preferably 110 to 180 ° C, and more preferably in the range of 120 ° C to 150 ° C. The one-component epoxy resin adhesive is preferably a low-temperature-curing epoxy resin adhesive. Also claimed is a method for bonding a first substrate and a second substrate with a one-component epoxy resin adhesive as described above, wherein with the epoxy resin adhesive bond between a surface of the first substrate and a surface of the second substrate is formed and the adhesive composite in a Temperature in the range of 1 10 ° C to 220 ° C, preferably 1 10 to 180 ° C, more preferably from 120 to 150 ° C, is cured.

The substrates may be any objects or parts. The one-component epoxy resin adhesive of the present invention can be used for bonding substrates of the same material or a different material.

The adhesives are particularly suitable for bonding substrates for automobiles or mounting or mounting modules for vehicles. Furthermore, the adhesives of the invention are also suitable for other applications. Particularly noteworthy are related applications in transport equipment such as ships, trucks, buses or rail vehicles, in the construction of consumer goods such as washing machines, but also in the construction sector, for example as stiffening structural adhesives.

The substrates to be bonded may be of any suitable material. The suitable materials are preferably metals and plastics such as ABS, polyamide, polyphenylene ethers, composite materials such as SMC, unsaturated polyester GRP, epoxy or acrylate composites. Preferred is the application in which at least one material is a metal. Particularly preferred use is the bonding of the same or different metals, especially in the shell in the automotive industry. The preferred metals are above all steel, in particular electrolytically galvanized, hot-dip galvanized, oiled steel, Bonazink-coated steel, and subsequently phosphated steel, as well as aluminum, in particular in the variants typically occurring in the automotive industry. By using the impact modifier of the invention in 1K epoxy adhesives as the impact modifier, an increase in toughness compared to the same epoxy resin adhesive but without the impact modifier of the invention is achieved, especially especially at curing temperatures in the range of 120 ° C to 150 ° C. Surprisingly, in particular an improved low temperature impact strength is achieved, for example at a temperature of -10 ° C or less, in particular at -30 ° C, for example.

Examples

The following are some examples which further illustrate the invention, but are not intended to limit the scope of the invention in any way. Unless otherwise indicated, all parts and percentages are by weight.

The following measurement methods were used to determine the parameters given below.

Determination of Isocvanatgehaltes

 The isocyanate content was determined in wt .-% by means of a back titration with excess di-n-butylamine and 0.1 M hydrochloric acid. All determinations were performed semi-manually on a Mettler-Toledo DL50 Graphix titrator with automatic potentiometric end point determination. For this purpose, in each case 600-800 mg of the sample to be determined were dissolved with heating in a mixture of 10 ml of isopropanol and 40 ml of xylene and then reacted with a solution of dibutylamine in xylene. Excess di-n-butylamine was titrated with 0.1 M hydrochloric acid and the isocyanate content was calculated therefrom.

Tensile strength Elongation at break and modulus of elasticity (DIN EN ISO 527)

An adhesive sample was pressed between two Teflon papers to a layer thickness of 2 mm. After 35 minutes of curing at 175 ° C., the Teflon papers were removed and the test specimens were punched to DIN standard. The specimens were measured under standard conditions at a pulling speed of 2 mm / min. The tensile strength, elongation at break and the modulus of elasticity 0.05-0.25% were determined in accordance with DIN EN ISO 527. Zuqscherfestiqkeit (LSS) (DIN EN 1465)

 Cleaned test specimens of steel H420-ZE (thickness 1, 5 mm) back-oiled with Anticorit PL 3802-39S were bonded to the adhesive on a bonding surface of 25 × 10 mm with glass beads as spacers in a layer thickness of 0.3 mm and placed under the adhesive hardened specified curing conditions.

Curing conditions: a) 10 minutes at 130 ° C oven temperature (undercuring), b) 10 minutes at 140 ° C oven temperature (undercuring), c) 60 minutes at 190 ° C oven temperature (overcuring). The tensile shear strength was determined on a tensile machine at a tensile speed of 10 mm / min in a 5-fold determination according to DIN EN 1465.

Angle peel strength (DIN 53281)

 Test panels a 130 x 25 mm were prepared from steel DC-04 + ZE (thickness 0.8 mm). Test panels were unwound at a height of 30 mm with a suitable punching machine (90 °). The cleaned surfaces of 100 × 25 mm back-lubricated with Anticorit PL 3802-39S were bonded to the adhesive with glass beads as spacers in a layer thickness of 0.3 mm and cured under standard conditions (35 min, 175 ° C. oven temperature). The peel strength was determined on a tractor with a tensile speed of 10 mm / min in a 3-fold determination as a peel force in N / mm in the range of the traverse path of 1/6 to 5/6 path length.

Schlaq peel strength (according to SO 1 1343)

The specimens were produced with the adhesive and steel DC04 + ZE with the dimensions 90 x 20 x 0.8 mm. The adhesive surface was 20 × 30 mm with a layer thickness of 0.3 mm and glass beads as spacers. The impact peel strength was measured in each case at the indicated temperatures (RT = 25 ° C., -30 ° C.) as a triple determination on a Zwick 450 impact pendulum. As impact peel strength, the average force in N / mm under the measurement curve of 25% to 90% according to ISO1 1343 is given. The adhesives were cured under various curing conditions: a) 10 minutes at 130 ° C oven temperature (undercure), b) 60 minutes at 190 ° C oven temperature (over cure). DSC

 Glass transition temperatures (Tg) were measured on a Mettler-Toledo 822e Differential Scanning Calorimeter (DSC) with the program segment below.

 Segment 1: Heating up from 25 to 175 ° C at a rate of 40 ° C / min. Segment 2: Hardening at 175 ° C for 20 min

 Segment 3: Cooling phase from 175 ° C to 20 ° C at a rate of - 40 ° C / min Segment 4: Equilibration phase 5 min at 20 ° C

 Segment 5: Heat-up phase from 20 ° C to 200 ° C at a rate of 20 ° C / min In segment 5, the glass transition temperature was reduced from the minimum of 1. Derivation function determined.

viscosity

 Viscosity measurements on the adhesives were made 1 d after preparation on an MCR 101 rheometer manufactured by Anton Paar oscillatory using a plate-plate geometry at a temperature of 25 ° C or 50 ° C with the following parameters: 5 Hz, 1 mm gap , Plate-to-plate distance 25 mm, 1% deformation. To assess the stability of the adhesives, the viscosity measurements were repeated after storage at 50 ° C. or 60 ° C. for one week and the percentage increase in viscosity resulting after storage was determined.

The following abbreviations are used: SB: standard hardening, UB: undercuring, OB: over hardening.

The following commercial products were used for the preparation of impact modifiers 1 to 14: Table 2:

Example 1: impact modifier SM1 (methoxyphenol [1, 0 eq.] As blocking agent, catalyst Bi)

 175 g of PolyTHF 2000, 175 g of poly bd R45V and 1.75 g of BHT as stabilizer were dewatered under reduced pressure at 90 ° C. for 1 h with minimal stirring. Subsequently, 70.56 g of isophorone diisocyanate (IPDI) and 0.046 g of dibutyltin dilaurate (DBTDL) were added. The reaction was carried out under vacuum at 90 ° C for 2 hours with moderate agitation to obtain an isocyanate-terminated polymer: Measured free NCO content: 3.1 1%.

To the resulting NCO-terminated polymer were added 0.655 g of catalyst Bi (Bi (III) neodecanoate-containing solution, 6% by weight of bismuth (III) in solution) and 37.84 g of 4-methoxyphenol (HQMME) and reacted for 3 h under vacuum at 1 10 ° C, the isocyanate groups. Measured free NCO content: (directly after preparation) 0.18%, (1 day after preparation) 0.13%.

Viscosity (1 day after preparation): 554 Pa ^* s at 25 ° C, 94 Pa ^* s at 50 ° C.

Example 2: Impact Modifier SM2 (Phenol [1.0 eq.] As

Blocking agent, catalyst Bi)

 175 g of PolyTHF 2000, 175 g of poly bd R45V and 1.75 g of BHT as stabilizer were dewatered under reduced pressure at 90 ° C. for 1 h with minimal stirring. Subsequently, 70.56 g of isophorone diisocyanate (IPDI) and 0.045 g of dibutyltin dilaurate (DBTDL) were added. The reaction was carried out under vacuum at 90 ° C for 2 hours with moderate agitation to obtain an isocyanate-terminated polymer: Measured free NCO content: 3.07%. To the resulting NCO-terminated polymer were added 0.643 g of catalyst Bi (Bi (III) neodecanoate-containing solution, 6% by weight of bismuth (III) in solution) and

Added 28.85 g of phenol and reacted for 3 h under vacuum at 1 10 ° C, the isocyanate groups. Measured free NCO content: (directly after production) 0.24%, (1 day after production) 0.19%.

Viscosity (1 day after preparation): 421 Pa ^* s at 25 ° C, 78 Pa ^* s at 50 ° C.

Example 3 Impact Modifier SM3 (2-Benzoxazolinone [1, 0 eq.] As Blocking Agent, Catalyst Bi)

 175 g of PolyTHF 2000, 175 g of poly bd R45V and 1.75 g of BHT as stabilizer were dewatered under reduced pressure at 90 ° C. for 1 h with minimal stirring. Subsequently, 70.56 g of isophorone diisocyanate (IPDI) and 0.045 g of dibutyltin dilaurate (DBTDL) were added. The reaction was carried out under vacuum at 90 ° C for 2 hours with moderate agitation to obtain an isocyanate-terminated polymer: Measured free NCO content: 3.05%.

To the NCO-terminated polymer obtained was added 0.660 g of Bi (Bi (III) neodecanoate catalyst solution, 6 wt% bismuth (III) in solution) and 41.25 g of 2-benzoxazolinone, and placed under vacuum at 1 for 3 h 10 ° C the Isocyanate groups reacted. Measured free NCO content: (directly after

Preparation) 0.13%, (1 day after preparation) 0.00%.

Viscosity (1 day after preparation): 422 Pa ^* s at 25 ° C, 82 Pa ^* s at 50 ° C. Example 4 Impact modifier SM4 (3,5 dimethylpyrazole [1, 0 eq.] As blocking agent, catalyst Bi)

 175 g of PolyTHF 2000, 175 g of poly bd R45V and 1.75 g of BHT as stabilizer were dewatered under reduced pressure at 90 ° C. for 1 h with minimal stirring. Subsequently, 70.56 g of isophorone diisocyanate (IPDI) and 0.045 g of dibutyltin dilaurate (DBTDL) were added. The reaction was carried out under vacuum at 90 ° C for 2 hours with moderate agitation to obtain an isocyanate-terminated polymer: Measured free NCO content: 3.08%.

To the resulting NCO-terminated polymer were added 0.643 g of Bi (Bi (III) neodecanoate catalyst-containing solution, 6 wt% bismuth (III) in solution) and 29.65 g of 3,5-dimethylpyrazole, and vacuumed for 3 hours at 1 10 ° C, the isocyanate groups reacted. Measured free NCO content: (directly after preparation) 0.02%.

Viscosity (1 day after preparation): 241 Pa ^* s at 25 ° C, 50 Pa ^* s at 50 ° C.

Comparative Example 1 Impact Modifier SM5 (4-Methoxyphenol as Blocking Agent [1, 0 eq.], DBTDL Catalyst)

175 g of PolyTHF 2000, 175 g of poly bd R45V and 1.75 g of BHT as stabilizer were dewatered under reduced pressure at 90 ° C. for 1 h with minimal stirring. Subsequently, 70.56 g of isophorone diisocyanate (IPDI) and 0.046 g of dibutyltin dilaurate (DBTDL) were added. The reaction was carried out under vacuum at 90 ° C for 2 hours with moderate agitation to obtain an isocyanate-terminated polymer: Measured free NCO content: 2.96%. To the NCO-terminated polymer obtained, 0.092 g of dibutyltin dilaurate (DBTDL) and 44.28 g of 4-methoxyphenol were added and the isocyanate groups were reacted for 5 h under vacuum at 110 ° C. Measured free NCO content: (directly after preparation) 0.39%; (1 day after preparation) 0.23%. Viscosity (1 day after preparation): 584 Pa ^* s at 25 ° C, 94 Pa ^* s at 50 ° C.

Comparative Example 2: Impact modifier SM6 (4-methoxyphenol

[1, 0 eq.] As blocking agent, di-n-butyl-bis (dodecyl-thio) tin catalyst)

 175 g of PolyTHF 2000, 175 g of poly bd R45V and 1.75 g of BHT as stabilizer were dewatered under reduced pressure at 90 ° C. for 1 h with minimal stirring. Subsequently, 70.56 g of isophorone diisocyanate (IPDI) and 0.046 g of dibutyltin dilaurate (DBTDL) were added. The reaction was carried out under vacuum at 90 ° C for 2 hours with moderate agitation to obtain an isocyanate-terminated polymer: Measured free NCO content: 2.91%.

0.1 16 g of di-n-butyl-bis (dodecylthio) tin and 36.1 g of 4-methoxyphenol were added to the resulting NCO-terminated polymer, and the isocyanate groups were reacted for 5 h under reduced pressure at 110 ° C. Measured free NCO content: (directly after production) 0.18%, (1 day after production) 0.15%. Viscosity (1 day after preparation): 672 Pa ^* s at 25 ° C, 104 Pa ^* s at 50 ° C.

Comparative Example 3 Impact Modifier SM7 (Only PolyTHF as Polyol, 4-Methoxyphenol [1, 0 eq] as Blocking Agent, Catalyst Bi)

350 g of PolyTHF 2000 were dewatered under reduced pressure at 90 ° C. for 1 h with minimal stirring. Subsequently, 77.00 g of isophorone diisocyanate (IPDI) and 0.047 g of dibutyltin dilaurate (DBTDL) were added. The reaction was carried out under vacuum at 90 ° C for 2 hours with moderate agitation to obtain an isocyanate-terminated polymer: Measured free NCO content: 3.1 1%.

To the obtained NCO-terminated polymer was added 0.670 g of catalyst Bi (Bi (III) neodecanoate-containing solution, 6% by weight of bismuth (III) in solution) and 39.23 g of 4-methoxyphenol and left under vacuum at 1 for 3 h 10 ° C, the isocyanate groups reacted. Measured free NCO content: (directly after preparation) 0.20%, (1 day after preparation) 0.07%.

Viscosity (1 day after preparation): 286 Pa ^* s at 25 ° C, 46 Pa ^* s at 50 ° C. Example 5: Impact Modifier SM8 (Poly BD by Hypro

3000x914 replaced, 4-methoxyphenol [1, 0 eq.] As blocking agent, catalyst Bi)

 175 g PolyTHF 2000, 175 g Hypro 3000X914 (Poly BD - Acrylonitrile Co-polymer from Emerald Performance Materials, Mn ca. 3000 g / mol, OH-functionality ca. 2.4, acrylonitrile content 14%) and 1, 75 g BHT as a stabilizer were dehydrated at 90 ° C. under vacuum for 1 h with minimal stirring. Subsequently, 65.66 g of isophorone diisocyanate (IPDI) and 0.045 g of dibutyltin dilaurate (DBTDL) were added. The reaction was carried out under vacuum at 90 ° C for 2 hours with moderate agitation to obtain an isocyanate-terminated polymer: Measured free NCO content: 2.99%.

To the resulting NCO-terminated polymer was added 0.646 g of catalyst Bi (Bi (III) neodecanoate-containing solution, 6 wt% bismuth (III) in solution) and 36.69 g of 4-methoxyphenol (HQMME) and allowed to stand for 2 h Vacuum at 1 10 ° C, the isocyanate groups reacted. Measured free NCO content: (directly after preparation) 0.13%, (1 day after preparation) 0.06%.

Viscosity (1 day after preparation): 71 1 Pa ^* s at 25 ° C, 101 Pa ^* s at 50 ° C. Examples 6 to 9

The impact modifiers SM1 to SM4 prepared in Examples 1 to 4 were each used to prepare adhesives according to Table 3 (SM1 for Example 6, SM2 for Example 7, SM3 for Example 8, SM4 for Example 9).

Compositions and proportions for a 1K epoxy adhesive containing one of the impact modifiers 1 to 4 are summarized in Table 3. SM-X refers to the above-prepared impact modifiers SM1, SM2, etc. Table 3

The respective adhesives were mixed in a batch size of 350 g in a planetary mixer. For this purpose, the mixing box was filled with the liquid components followed by the solid components, the accelerator was not added, and mixed with gentle heating at temperatures not higher than 40 ° C. After obtaining a homogeneous mixture, the heater was turned off and the accelerator was mixed with high shear (about 80 rpm, level 3.5). Subsequently, the adhesive obtained was filled into cartridges and stored at room temperature.

Table 4 shows the results of the evaluation of the resulting adhesives with the impact modifiers [PolyTHF / PolyBD R45V (1: 1), IPDI (0.98 eq.), HQMME (1, 0 eq.)] With various blocking agents Table 4

Example 10

The preparation of the impact modifier SM1 according to Example 1 was repeated, except that the proportion of blocking agent HQMME (4-methoxyphenol) based on the amount of isocyanate groups of the isocyanate-terminated polymer as indicated in Table 5 in SM 9 to 1.2 equivalents (NCO / OH equivalent ratio) was increased. With SM9, an adhesive was produced analogously to Example 6. Table 5 compares the properties of the resulting adhesives of Example 10 and Example 6. It shows that the one-component epoxy adhesive compositions comprising the impact modifiers according to the invention have high strengths and tensile strengths without the need to use the blocking agent in large excess. Table 5:

Comparative Examples 4 and 5

Example 6 was repeated except that the impact modifiers SM5 (for Comparative Example 4) and SM6 (for Comparative Example 5) prepared in Comparative Examples 1 and 2 were used instead of the impact modifier SM1.

Table 6 shows the evaluation results for the adhesives thus prepared, in which the results for Example 6 are also included. Table 6 shows the effect of the catalyst on the blocking reaction and the properties of the final epoxy adhesive with the included impact modifier (PolyTHF (50), PolyBD (50), IPDI (0.98 eq), HQMME (1, 0 eq)). Table 6:

The one-component epoxy resin adhesive composition comprising the impact modifier of the invention (Example 6) has high strengths and tensile strengths, in particular a high impact peel strength at low temperatures, and good storage stability.

Examples 11 and 12

 In Examples 1 1 and 12, formulations with the impact modifiers SM9 and SM10 were prepared according to Example 6.

SM9 and SM10 were prepared analogously to SM1, whereas in SM9 and SM10, in contrast to SM1 1, 2 eq. 4-methoxyphenol were used as blocking agents. In addition, in SM10, the amount of catalyst Bi (Bi (III) neodecanoate containing solution, 6 wt% of bismuth (III) in solution) was increased from 0.14% to 0.5% to the effect of the amount of catalyst used Bi in the blocking step of impact modifier synthesis. It was found that with 0.5 percent by weight the maximum of the performance / impact peel strength achievable with catalyst Bi had already been exceeded. An amount of solution containing 0.14% of catalyst Bi (Bi (III) neodecanoate, 6% by weight of bismuth (III) in solution) corresponds to an amount of 0.05% by weight of bismuth catalyst or Bi (III ) neodecanoate (Bi-Cat.) and an amount of 0.5% of catalyst Bi corresponds to an amount of 0.18 wt .-% bismuth catalyst or Bi (III) neodecanoate. Table 7:

Example 13 and Comparative Example 6

Example 6 was repeated, except that instead of impact modifier SM1, the impact modifiers prepared in Example 5 and in Comparative Example 3 were used. toughness modifiers SM8 (for Example 13) and SM7 (for Comparative Example 6) were used.

Table 8 shows the evaluation results for the adhesives thus prepared, in which the results for Example 6 are also included.

Table 8

Comparative Examples 7 to 10

Example 1 was repeated except that instead of 4-methoxyphenol the blocking agents shown in Table 9 were used. The impact modifiers SM1 1 to SM14 were obtained. For the impact modifiers SM1 1 and SM12, virtually no blocking of the isocyanate-terminated polymer was achieved so that these impact modifiers were not further investigated. The impact modifiers SM13 and SM14 were used to produce adhesives as in Example 6, except that impact modifier SM1 has been replaced by SM13 or SM14. The resulting adhesives did not show sufficient storage stability (hardening after 1 week at 50 ° C) and therefore were not further investigated.

Table 9

 Comp Ex. Comp Ex. Comp Ex. Comp Ex.

 7 8 9 10

 Impact resistance SM1 1 SM12 SM13 SM14 modifier

 Dodecane-ethylaceto-2-mercapto-tetramethyl-

blocking agents

 thiol acetate pyridine guanidine

NCO content of <0.25%

after 3h implementation no no yes yes for blocking

 Stability 1w 50 ° C - - no no

Claims

claims

Impact modifier, which is an isocyanate-terminated polymer whose isocyanate groups by reaction with a

Blocking agents are partially or completely blocked, available through

 A) Reaction of a) two or more polyols comprising a1)

 Polytetramethylenetherglycol and a2) at least one hydroxy-terminated polybutadiene, wherein the total amount of

 Polytetramethylene ether glycol and hydroxy-terminated

 Polybutadiene at least 95 wt .-%, based on the

 Total weight of the polyols, and b) at least one acyclic aliphatic or cycloaliphatic polyisocyanate in the presence c) at least one catalyst to form an isocyanate-terminated polymer, and

 B) reacting the isocyanate-terminated polymer obtained in step A) with d) at least one blocking agent selected from the group consisting of phenols, 2-benzoxazolinones and pyrazoles in the presence of e) at least one organic bismuth catalyst to form the partially or fully blocked isocyanate -terminated polymer.

Impact modifier according to claim 1, characterized

in that b) comprises or is at least one acyclic aliphatic or cycloaliphatic polyisocyanate hexamethylene diisocyanate and / or isophorone diisocyanate.

Impact modifier according to at least one of

preceding claims, characterized in that the c) at least one catalyst in step A) comprises or is an organic tin catalyst, preferably dibutyltin dilaurate. Impact modifier according to at least one of

preceding claims, characterized in that the e) comprises or is at least one organic bismuth catalyst bismuth (III) - neodecanoate.

Impact modifier according to at least one of

preceding claims, characterized in that the proportion of c) at least one catalyst in step A) in the range of 0.5 wt .-% to 0.001 wt .-%, preferably from 0.025 wt .-% to 0.005 wt .-%, based on the total mass of the blocked

Impact modifier, lies.

Impact modifier according to at least one of

preceding claims, characterized in that the proportion of the catalytically active center, in particular bismuth (III), of the e) at least one organic bismuth catalyst in step B) in the range of 0.5 wt .-% to 0.002 wt .-%, preferably from 0.1% to 0.004% by weight, more preferably from 0.03% to 0.005% by weight, based on the total mass of the blocked one

Impact modifier, lies.

Impact modifier according to at least one of

preceding claims, characterized in that the d) at least one blocking agent is selected from phenol, cresol, resorcinol, pyrocatechol, 3-pentadecenylphenol, nonylphenol, 3-methoxyphenol, 4-methoxyphenol, reacted with styrene or dicyclopentadiene phenols, bisphenol A, bisphenol F , 2,2'-diallyl-bisphenol-A, 2-benzooxazolinone and 3,5-dimethylpyrazole, with 4-methoxyphenol being preferred.

Impact modifier according to at least one of

preceding claims, characterized in that the

Weight ratio of a1) polytetramethylene ether glycol to a2) the at least one hydroxy-terminated polybutadiene in the range of 70/30 to 30/70, preferably from 60/40 to 40/60, and most preferably in the range of about 50/50, is located.

Impact modifier according to at least one of

preceding claims, characterized in that in step B) the equivalent ratio of the isocyanate groups of the isocyanate-terminated polymer to the isocyanate-reactive groups of the blocking agent in the range of 1, 5 to 0.7, preferably from 1, 2 to 0.8, and most preferably close to 1: 1.

Impact modifier according to at least one of

preceding claims, characterized in that the isocyanate-terminated polymer formed in step A) has an average of 2 to 4 polyol units per polymer.

Impact modifier according to at least one of

preceding claims, characterized in that the

Hydroxy-terminated polybutadiene is a number average of

Molecular weight (Mn) in the range of 2000 to 4000 g / mol.

A process for preparing an impact modifier according to any one of claims 1 to 11, comprising

A) the reaction of a) two or more polyols comprising a1) polytetramethylene ether glycol and a2) at least one hydroxy-terminated polybutadiene, wherein the total amount of

 Polytetramethylene ether glycol and hydroxy-terminated

 Polybutadiene at least 95 wt .-%, based on the

Total weight of the polyols, and b) at least one acyclic aliphatic or cycloaliphatic polyisocyanate in the presence c) at least one catalyst to form an isocyanate-terminated polymer, and the reaction of the isocyanate-terminated polymer obtained in step A) with d) at least one

 Blocking agents selected from the group consisting of phenols, 2-benzoxazolinones and pyrazoles in the presence e) of at least one organic bismuth catalyst to form the partially or completely blocked isocyanate-terminated polymer.

Use of an impact modifier according to any one of claims 1 to 11 in a one-component epoxy resin adhesive for bonding at a curing temperature in the range of 110 ° C to 220 ° C, preferably 110 to 180 ° C, more preferably 120 to 150 ° C.

One-component epoxy resin adhesive comprising

a) at least one epoxy resin,

b) at least one hardener for epoxy resins and

c) an impact modifier according to any one of

 Claims 1 to 1 1,

wherein the proportion of the impact modifier is preferably in a range of 5 to 60% by weight, more preferably 10 to 25% by weight.

A method of bonding a first substrate and a second substrate with a one-component epoxy adhesive

Claim 14, wherein with the epoxy resin adhesive, an adhesive bond between a surface of the first substrate and a surface of the second substrate is formed and the adhesive composite at a temperature in the range of 1 10 ° C to 220 ° C, preferably 1 10 to 180 ° C, especially preferably from 120 to 150 ° C, is cured.