Thermosetting epoxy resin composition with good storage stability suitable for low curing temperature

Abstract

The present invention relates to a thermosetting epoxy resin composition comprising a dihydrazide as curing agent, in combination with an accelerator of an imidazolium salt as curing agent, the molar ratio of curing agent to accelerator being 6-120. The compositions are characterized by good storage stability and low cure temperature. The epoxy resin composition is particularly suitable for use as a vehicle body adhesive.

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of thermosetting one-component epoxy resin compositions, in particular those compositions used as a body adhesive. BACKGROUND

[0002] Thermosetting epoxy resin compositions have been known for a long time. For a long time, efforts have been made to remedy or at least significantly reduce the great disadvantage of epoxy resin compositions, namely their brittleness, with the effect that cured epoxy resin compositions crack or are destroyed under impact stress. This has been attempted by the addition of impact modifiers or by chemical modification of the epoxy resin.

[0003] An important field of use of thermosetting epoxy resin compositions is in the construction of motor vehicles, in particular in the joining of vehicle bodies. After application of the epoxy resin composition, the vehicle body is heated in a cathodic electrocoating oven, whereby the thermosetting epoxy resin composition is cured. WO 2019081581 A1 describes a thermosetting epoxy resin composition used as a body adhesive and for the production of structural foams.

[0004] In order to make rapid curing possible, accelerators can be used together with the heat-activatable curing agent of the epoxy resin. Examples of known classes of accelerators include latent imidazoles and amine-boron trifluoride complexes.

[0005] However, there is currently an effort on the market to reduce the temperature of the cathodic electrocoating oven. Therefore, there is a great need on the market for thermosetting epoxy resin compositions which cure even at relatively low temperatures, i.e. at temperatures of 130 to 140°C, even after a short time, usually 10 to 15 minutes. If, for example, aromatic ureas are used for this purpose, which are significantly more reactive due to their structure, this leads to serious problems in terms of storage stability of the thermosetting epoxy resin composition. There is therefore a need for thermosetting one-component epoxy resin compositions which cure at lower temperatures, but have sufficient storage stability. SUMMARY

[0006] It is therefore an object of the present invention to provide a storage-stable thermosetting one-component epoxy resin composition which has sufficient mechanical properties, in particular lap shear strength and impact peel performance, after a short curing time at lower temperatures, in particular after 10 minutes at 140°C.

[0007] This object is surprisingly achieved by the thermosetting one-component epoxy resin composition as claimed in claim 1. The inventive epoxy resin composition has a particularly good usability as a one-component thermosetting adhesive, in particular as a thermosetting one-component body adhesive in the construction of motor vehicles. DETAILED DESCRIPTION

[0008] The present invention relates to a thermosetting one-component epoxy resin composition comprising

[0009] a) at least one epoxy resin A having an average of more than one epoxy group per molecule;

[0010] b) at least one epoxy resin curing agent B, wherein the curing agent B is a dihydrazide, preferably selected from the group consisting of aromatic dicarboxylic acid dihydrazides B1 and aliphatic dicarboxylic acid dihydrazides B2; and

[0011] c) at least one accelerator C for the at least one curing agent B, which is an imidazole of formula (V) salt:

[0012]

[0013] wherein

[0014] R1is an organic radical having 1 to 20 C atoms,

[0015] R2, R3, R4and R5are each a H atom or an organic radical having 1 to 20 C atoms,

[0016] X is an anion, and

[0017] n is 1, 2 or 3, preferably 1 ;

[0018] the imidazole of formula (V) salt is selected from the group consisting of 1 -ethyl-3-methylimidazolium ethylsulfate, 1 -ethyl-3-methylimidazolium diethylphosphate, 1 -butyl-3-methylimidazolium and 1 -ethyl-3-methylimidazolium acetate, most preferably 1 -ethyl-3-methylimidazolium ethylsulfate.

[0019] The molar ratio (B / C) of the at least one epoxy resin curing agent B to the at least one accelerator C is 6 - 120, preferably 10 - 100, more preferably 12 - 75.

[0020] Herein, the term "independently" used in connection with substituents, residues or groups shall be interpreted that substituents, residues or groups of the same name in the same molecule can occur simultaneously with different meanings.

[0021] Herein, the prefix "poly" in a substance name such as "polyol", "polyisocyanate", "polyether" or "polyamine" indicates that the respective substance contains in formal sense more than one functional group of the name occurring in the name per molecule.

[0022] In the present text, "molecular weight" is understood to mean the molar mass of a molecule in g / mole. "Average molecular weight" is understood to mean the number average molecular weight M n which is usually determined by means of GPC with polystyrene as standard.

[0023] "A primary hydroxyl group" means an OH group bonded to a carbon atom having two hydrogens.

[0024] In the present text, the term "primary amino group" means an NH2 group bonded to one organic group, while the term "secondary amino group" means an NH group bonded to two organic groups, which can also together be part of a ring. Thus, an amine having one primary amino group is referred to as a "primary amine", an amine having a secondary amino group is correspondingly referred to as a "secondary amine" and an amine having a tertiary amino group is referred to as a "tertiary amine".

[0025] In the present text, "room temperature" means a temperature of 23°C.

[0026] The epoxy resin A having an average of more than one epoxy group per molecule is preferably a liquid epoxy resin or a solid epoxy resin. The term "solid epoxy resin" is very well known to the person skilled in the art of epoxides and is used in contrast to "liquid epoxy resin". Solid resins have a glass transition temperature above room temperature, meaning that they can be comminuted at room temperature to produce a free-flowing powder.

[0027] The preferred epoxy resin has the formula (II)

[0028] Here the substituents R' and R" are independently H or CH3.

[0029] In solid epoxy resins, the index s has a value > 1.5, in particular 2 to 12.

[0030] Such solid epoxy resins are commercially available, for example, from Dow or Huntsman or Hexion.

[0031] Compounds of the formula (II) having an index s of 1 to 1.5 are referred to by the person skilled in the art as semi-solid epoxy resins. For the present application, they are likewise considered to be solid resins. However, the preferred solid epoxy resins are epoxy resins in the narrower sense, i.e. epoxy resins having an index s with a value > 1.5.

[0032] In liquid epoxy resins, the index s has a value of less than 1. Preferably, s has a value of less than 0.2.

[0033] Thus, preferred are the diglycidyl ethers of bisphenol A (DGEBA), the diglycidyl ethers of bisphenol F and the diglycidyl ethers of bisphenol A / F. Such liquid resins are commercially available, for example, as Araldite® GY 250, Araldite® PY 304, Araldite® GY 282 (Huntsman) or D.E.R.™ 331 or D.E.R.™ 330 (Dow) or Epikote 828 (Hexion).

[0034] Further suitable epoxy resins A are so-called epoxy novolacs. More particularly, these are phenol or cresol epoxy novolacs.

[0035] Such epoxy resins are commercially available under the trade names EPN or ECN and Tactix® from Huntsman or from the D.E.N.™ product line from Dow Chemical.

[0036] The epoxy resin A is preferably an epoxy resin of the formula (II), in particular a liquid epoxy resin of the formula (II).

[0037] In a particularly preferred embodiment, the thermosetting one-component epoxy resin composition contains both at least one liquid epoxy resin of the formula (II) with s < 1, in particular less than 0.2, and at least one solid epoxy resin of the formula (II) with s > 1.5, in particular 2 to 12.

[0038] The proportion of the epoxy resin A is preferably 10 to 60% by weight, more preferably 30 to 60% by weight, most preferably 40 to 55% by weight, based on the total weight of the thermosetting one-component epoxy resin composition.

[0039] It is further advantageous when 50 to 100% by weight, in particular 80 to 100% by weight, of the epoxy resin A is a liquid epoxy resin as described above.

[0040] It is further advantageous when 0 to 30% by weight, in particular 0 to 20% by weight, more preferably 5 to 15% by weight, of the epoxy resin A is a solid epoxy resin as described above.

[0041] The composition according to the application also contains at least one epoxy resin curing agent B. The curing agent B is a dihydrazide which is preferably selected from the group consisting of aromatic dicarboxylic acid dihydrazides B1 and aliphatic dicarboxylic acid dihydrazides B2.

[0042] If the curing agent B is an aromatic dicarboxylic acid dihydrazide B1, it is preferably selected from the group consisting of isophthalic acid dihydrazide and / or terephthalic acid dihydrazide, preferably isophthalic acid dihydrazide.

[0043] Suitable dihydrazides are commercially available, for example, from Otsuka Chemical Co., Ltd under the trade name Ajicure® (from Ajinomoto Fine-Techno Co., Inc.) and under the trade name Technicure® (from A&C Catalysts).

[0044] Preferably, the curing agent B is an aliphatic dicarboxylic acid dihydrazide B2, preferably selected from glutaric dihydrazide, adipic dihydrazide, pimelic dihydrazide, 8,12-icosadienoic acid 1,20-dihydrazide and 4-isopropyl-2,5-dioxoimidazolidine-1,3-di(propanehydrazide).

[0045] Preferably adipic dihydrazide, 8,12-icosadienoic acid 1,20-dihydrazide (UDH) and 4-isopropyl-2,5-dioxoimidazolidine-1,3-di(propanehydrazide) (VDH). Most preferred is adipic dihydrazide.

[0046] Suitable dihydrazides are commercially available, for example, from Otsuka Chemical Co., Ltd under the trade name Ajicure® (from Ajinomoto Fine-Techno Co., Inc.) and under the trade name Technicure® (from A&C Catalysts).

[0047] The comparison of Table 2 and Table 3 shows that compositions containing aromatic dicarboxylic acid dihydrazides exhibit lower lap shear strength (LSS) values than compositions containing aliphatic dicarboxylic acid dihydrazides. This is shown, for example, in the comparison of E5 with E1 or E7 with E2.

[0048] Preferably, the at least one curing agent B is present in the thermosetting epoxy resin composition in an amount that the molar ratio of curing agent B to epoxy resin A is 300 - 550 mmol / mol, preferably 400-500 mmol / mol, more preferably 425-475 mmol / mol.

[0049] The ratio of the proportion of epoxy groups of the epoxy resin A in mol to the sum of curing agent B1 and curing agent B2 in mol (A / (B1+B2)) is preferably 3-5, in particular 3.5-4.5. This is advantageous because in this range particularly advantageous values for the mechanical properties, in particular the lap shear strength and the impact peel, of the cured composition are obtained.

[0050] It can also be advantageous when more than 80 wt.-%, preferably more than 90 wt.-%, in particular more than 95 wt.-%, particularly preferably more than 98 wt.-%, most preferably more than 99 wt.-%, based on the total weight of the thermosetting one-component epoxy resin composition, of the molecules capable of acting as a curing agent for the epoxy resin at temperatures of 100 to 220 °C are molecules of the curing agents B1 and B2.

[0051] It is also advantageous when the thermosetting one-component epoxy resin composition comprises a minimum amount of dicyandiamide. If the epoxy resin composition comprises dicyandiamide, the weight ratio of the total amount of the curing agent B1 and the curing agent B2 to the dicyandiamide ((B1 + B2) / dicyandiamide) is ≥ 0.5, ≥ 0.75, ≥ 1, ≥ 2, ≥ 5, in particular ≥ 10, preferably ≥ 50, more preferably ≥ 100.

[0052] The composition according to the application also contains at least one accelerator C for at least one curing agent B, which is an imidazole of the formula (V) salt:

[0053]

[0054] wherein

[0055] R1is an organic radical having 1 to 20 C atoms,

[0056] R2, R3, R4and R5are each a hydrogen atom or an organic radical having 1 to 20 C atoms,

[0057] X is an anion, and

[0058] n is 1, 2 or 3, preferably 1.

[0059] Preferably, the anion X is selected from the group consisting of alkylsulfates; alkylsulfonates; halides, more particularly chloride, bromide and iodide; thiocyanates; dicyanamides; carboxylates; phosphates, more particularly dimethylphosphates and diethylphosphates; and phosphonates.

[0060] More preferably, the anion X is selected from the group consisting of alkylsulfates; halides, more particularly chloride; carboxylates; phosphates, more particularly dimethylphosphates.

[0061] Even more preferably, the anion X is selected from the group consisting of alkylsulfonates.

[0062] Preferred alkylsulfates have the formula R a OSO3 - wherein R a is a C1-C12 alkyl group or a C5-C12 aryl group, preferably a C1-C6 alkyl group or a C6 aryl group, most preferably a C2 alkyl group (ethylsulfate).

[0063] The comparison of Table 3 and Table 4 also shows that compositions containing C1 exhibit higher impact peel values and lower viscosity increase than compositions containing C2-C4. This is shown, for example, in the comparison of E5 with E9, E11 and E12.

[0064] The preferred halide is chloride.

[0065] The preferred phosphate is a dialkylphosphate of the formula R b R c PO4 - wherein R b and R c are independently of each other a C1-C6 alkyl group; more particularly R b and R c are identical alkyl groups, most preferably dimethylphosphate and diethylphosphate, in particular diethylphosphate.

[0066] The preferred carboxylate is a carboxylate of the formula R d COO - wherein R d is a C1-C20 alkyl group or a C6-C10 aryl or aralkyl group, preferably a C1-C8 alkyl group, more particularly acetate.

[0067] Particularly preferred anions X are selected from the group consisting of acetate, diethylphosphate, chloride and ethylsulfate.

[0068] In formula (V) R1and R3are preferably independently of each other an organic group having 1 to 10 C atoms. More particularly R1and R3are aliphatic groups, more particularly aliphatic groups without additional heteroatoms, such as alkyl groups. It is particularly preferred that R1and R3are independently of each other a C1-C10 or C1-C4 alkyl group. It is very preferred that R1is a methyl group and R3is an ethyl group, or R1is a methyl group and R3is a butyl group.

[0069] In formula (V) R2, R4and R5, preferably independently, are a H atom or an organic group having 1 to 10 C atoms; more particularly R2, R4and R5are a H atom or an aliphatic group. It is particularly preferred that R2, R4and R5, independently of each other, are a H atom or an alkyl group; more particularly R2, R4and R5, independently of each other, are a H atom or a C1-C4 alkyl group. It is very preferred that R2, R4and R5are each a H atom. Preferably, n is 1.

[0070] X is preferably one of the above and preferred anions, very preferably selected from the group consisting of acetate, diethylphosphate, chloride and ethylsulfate.

[0071] Most preferably, the imidazolium salt of formula (V) is selected from the group consisting of 1-ethyl-3-methylimidazolium Ethylsulfate, 1 -ethyl-3-methylimidazole Diethylphosphate, 1 -butyl-3-methylimidazolium chloride and 1 -ethyl-3-methylimidazole acetate.

[0072] Suitable imidazoles of formula (V) The salts are commercially available, for example from BASF under the trade name Basionics®.

[0073] The molar ratio (B / C) of the at least one epoxy resin curing agent B to the at least one accelerator C is 6 - 120, preferably 10 - 100, more preferably 12 - 75.

[0074] It can be seen from the results in Table 2 that a molecular ratio (B / C) of more than 120 leads to insufficient lap shear strength values. This is shown, for example, in the comparison of E1 and E2 with R5. Likewise, the results in Table 3 show that a molecular ratio (B / C) of more than 120 leads to insufficient lap shear strength values. This is shown, for example, in the comparison of E1 and E2 with R5.

[0075] It can also be seen from the results in Table 4 that a molecular ratio (B / C) of more than 120 leads to insufficient impact peel values. This is shown, for example, in the comparison of E9 - E10 with R10, E11 with R11 and E12 with R12.

[0076] Table 3 also shows that a molecular ratio (B / C) of less than 6 leads to a high increase in viscosity. This is shown, for example, in the comparison of E3 - E8 with R9.

[0077] It can be preferred if the molar ratio (B / C) of the at least one epoxy resin curing agent B to the at least one accelerator C is 12 - 25, preferably 14 - 20. This ratio is advantageous in terms of higher lap shear strength values. This is shown, for example, in Table 3 in the comparison of E6 - E7 with E8 and E3 - E5. This is also shown in Table 1 in the comparison of E2 with E1.

[0078] It can also be preferred if the molar ratio (B / C) of the at least one epoxy resin curing agent B to the at least one accelerator C is 25 - 75, preferably 26 - 70, more preferably 40 - 70.

[0079] Such a ratio is advantageous in terms of a low increase in viscosity after storage. This is shown, for example, in Table 3 in the comparison of E3 - E5 with E6 - E8.

[0080] The amount of dicyandiamide is preferably less than 5 wt.-%, less than 3 wt.-%, less than 2 wt.-%, in particular less than 1 wt.-%, preferably less than 0.5 wt.-%, more preferably less than 0.3 wt.-%, most preferably less than 0.1 wt.-%, based on the total weight of the epoxy resin composition. More preferably, the thermosetting one-component epoxy resin composition does not comprise any dicyandiamide.

[0081] It is also preferred, if the thermosetting one-component epoxy resin composition contains other epoxy resin accelerators than the at least one accelerator C mentioned before in an amount of less than 0.5 wt.-%, less than 0.1 wt.-%, less than 0.05 wt.-%, in particular less than 0.01 wt.-%, preferably less than 0.001 wt.-%, based on the total weight of the epoxy resin composition. More preferably, the thermosetting one-component epoxy resin composition does not comprise any other epoxy resin accelerators than the at least one accelerator C mentioned before. Such other epoxy resin accelerators are preferably selected from the group consisting of substituted ureas, imidazoles and blocked amines.

[0082] The amount of accelerator C is advantageously 0.5 - 5.0 wt.-%, in particular 0.75 - 3.0 wt.-%, preferably 1.0 - 2.0 wt.-%, based on the weight of the epoxy resin A.

[0083] It is also preferred, if the at least one accelerator C is present in the one-component thermosetting epoxy resin composition in a molar ratio of accelerator C to epoxy resin A of 5 - 95 mmol / mol, preferably 10 - 50 mmol / mol, more preferably 15 - 25 mmol / mol.

[0084] The ratio of accelerator C in g per mol of epoxy groups of the epoxy resin A is preferably 0.5 - 9.0 g / mol of epoxy groups, in particular 0.75 - 7.0 g / mol of epoxy groups, more preferably 1.0 - 4.5 g / mol of epoxy groups, more preferably 1.5 - 3.0 g / mol of epoxy groups, most preferably 2.0 - 2.5 g / mol of epoxy groups.

[0085] The one-component thermosetting epoxy resin composition preferably comprises at least one toughness improver D. The toughness improver D can be solid or liquid.

[0086] More particularly, the toughness improver D is selected from the group consisting of end-capped polyurethane polymers D1, liquid rubbers D2 and core-shell polymers D3. The toughness improver D is preferably selected from the group consisting of end-capped polyurethane polymers D1 and liquid rubbers D2. Particularly preferred are end-capped polyurethane polymers D1.

[0087] If the toughness improver D is an end-capped polyurethane prepolymer D1.

[0088] Preferably, the end-capped polyurethane polymer D1 is capped with a blocking group which is removed at temperatures above 100°C.

[0089] Preferred blocking groups are in particular first of all phenols or bisphenols. Preferred examples of such phenols and bisphenols are in particular phenol, cresol, resorcinol, catechol, cardanol (3-pentadecenylphenol from cashew nut shell liquid), nonylphenol, phenols which have reacted with styrene or dicyclopentadiene, bisphenol A, bisphenol F and 2,2'-diallylbisphenol A.

[0090] The end-capped polyurethane prepolymer is prepared from a linear or branched polyurethane prepolymer which is terminated by isocyanate groups with one or more isocyanate-reactive compounds. If two or more such isocyanate-reactive compounds are used, the reaction can be carried out sequentially or with a mixture of these compounds.

[0091] The reaction is preferably carried out in such a way that the one or more isocyanate-reactive compounds are used stoichiometrically or in stoichiometric excess in order to ensure that all NCO groups have been converted.

[0092] The polyurethane prepolymer having isocyanate end groups can be prepared from at least one di- or triisocyanate and from a polymer Q having terminal amino, thiol or hydroxyl groups PM and / or from an optionally substituted polyphenol Q PP .

[0093] Suitable diisocyanates are aliphatic, cycloaliphatic, aromatic or araliphatic diisocyanates, in particular commercially available products such as methylene diphenyl diisocyanate (MDI), hexamethylene diisocyanate (HDI), toluene diisocyanate (TDI), toluene diamine diisocyanate (TODI), isophorone diisocyanate (IPDI), trimethylhexamethylene diisocyanate (TMDI), 2,5- or 2,6-bis(isocyanatomethyl)bicyclo[2.2.1]heptane, naphthalene 1,5-diisocyanate (NDI), dicyclohexylmethyl diisocyanate (H 12 MDI), p-phenylene diisocyanate (PPDI), m-tetramethylxylylene diisocyanate (TMXDI) and the like, and their dimers. Preferably, HDI, IPDI, MDI or TDI.

[0094] Suitable triisocyanates are trimers or biurets of aliphatic, cycloaliphatic, aromatic or araliphatic diisocyanates, in particular biurets of the isocyanurates and diisocyanates described in the previous paragraph. Of course, suitable mixtures of di- or triisocyanates can also be used.

[0095] Particularly suitable polymers Q having terminal amino, thiol or hydroxyl groups are PMis a polymer Q having two or three terminal amino, thiol or hydroxyl groups PM .

[0096] polymer Q PM Advantageously, the NCO-reactive groups have an equivalent weight of 300 to 6000, in particular of 600 to 4000, preferably of 700 to 2200 g / equivalent.

[0097] preferred polymer Q PM is a polyol having an average molecular weight of 600 to 6000 Dalton, selected from the group consisting of polyethylene glycol, polypropylene glycol, polyethylene glycol-polypropylene glycol block polymers, polybutylene glycol, hydroxyl-terminated polybutadiene, hydroxyl-terminated butadiene-acrylonitrile copolymers and mixtures thereof.

[0098] particularly preferred polymer Q PM is an a,w-dihydroxypolyalkylenediol having C2-C6-alkylene groups or having mixed C2-C6-alkylene groups and terminated with amino, thiol or preferably hydroxyl groups. Particularly preferred are polypropylene glycol or polybutylene glycol. Also particularly preferred are hydroxyl-terminated polyoxybutylene.

[0099] particularly suitable polyphenol Q PP is a bisphenol, a triphenol and a tetraphenol. This is understood to mean not only straight-chain phenols, but optionally also substituted phenols. The nature of the substitution can vary greatly. More particularly, this is understood to mean substitution directly on the aromatic ring to which the phenolic OH group is bonded. Phenol is additionally understood to mean not only monocyclic aromatic compounds, but also polycyclic or fused aromatic or heteroaromatic compounds having a phenolic OH group directly on the aromatic or heteroaromatic system.

[0100] In a preferred embodiment, the polyurethane prepolymer is prepared from at least one di- or triisocyanate and from a polymer Q having terminal amino, thiol or hydroxyl groups PM . The polyurethane prepolymer is prepared in a manner known to the person skilled in the art of polyurethanes, in particular by using a di- or triisocyanate in chemical excess with respect to the amino, thiol or hydroxyl groups of the polymer Q PM .

[0101] The polyurethane prepolymer having isocyanate end groups preferably has elastic characteristics. It preferably exhibits a glass transition temperature Tg of less than 0°C.

[0102] The toughness improver D can be a liquid rubber D2. This can be, for example, a carboxyl- or epoxy-terminated polymer.

[0103] In a first embodiment, such liquid rubbers can be carboxyl or epoxy-terminated acrylonitrile / butadiene copolymers or derivatives thereof. Such liquid rubbers are commercially available, for example, under the Hypro / Hypox® CTBN and CTBNX and ETBN trade names from Emerald Performance Materials. Suitable derivatives are, in particular, elastomer-modified prepolymers with epoxy groups, such as the Polydis® product line, in particular from the Polydis® 36 product line, by Struktol® (Schill + Seilacher Gruppe, Germany) or the Albipox product line (Evonik, Germany) are commercially marketed.

[0104] In a second embodiment, such liquid rubbers can be polyacrylate liquid rubbers, which are fully miscible with the liquid epoxy resin and only separate during the curing process of the epoxy resin matrix to form microdroplets. Such polyacrylate liquid rubbers are commercially available, for example, under the Dowlex® 20208-XPA trade name from Dow.

[0105] Of course, mixtures of liquid rubbers, in particular mixtures of carboxyl or epoxy-terminated acrylonitrile / butadiene copolymers or derivatives thereof, can also be used.

[0106] In a third embodiment, the toughness improver D can be a core-shell polymer D3. Core-shell polymers consist of an elastic core polymer and a rigid shell polymer. Particularly suitable core-shell polymers consist of a core of an elastic acrylate or butadiene polymer surrounded by a rigid shell of a rigid thermoplastic polymer. This core-shell structure either forms spontaneously due to the segregation of block copolymers or is defined by emulsion or suspension polymerization with subsequent grafting. Preferred core-shell polymers are those known as MBS polymers, which are commercially available under the Clearstrength™ trade name from Arkema, under Paraloid™ from Dow or under F-351™ from Zeon.

[0107] Preferably, the ratio of the toughness improver D, in particular of the end-capped polyurethane polymer D1, is 15 to 45 wt.-%, in particular 20 to 40 wt.-%, in particular 22.5 to 35 wt.-%, in particular 25 to 35 wt.-%, more preferably 27.5 to 32.5 wt.-%, based on the total weight of the thermosetting one-component epoxy resin composition.

[0108] This is advantageous because it results in high impact peel values, while at the same time high lap shear strength values.

[0109] In a further preferred embodiment, the composition additionally comprises at least one filler F. Preferred here are mica, talc, kaolin, wollastonite, feldspar, syenite, chlorite, bentonite, montmorillonite, calcium carbonate (precipitated or ground), dolomite, quartz, silica (fused or precipitated), cristobalite, calcium oxide, aluminium hydroxide, magnesium oxide, hollow ceramic beads, hollow glass beads, hollow organic beads, glass beads, coloured pigments. Particularly preferred are fillers selected from the group consisting of calcium carbonate, calcium oxide and fumed silica.

[0110] Advantageously, the total proportion of the total filler F is 5 to 40% by weight, preferably 10 to 30% by weight, based on the total weight of the thermosetting one-component epoxy resin composition.

[0111] In a further preferred embodiment, the composition additionally comprises at least one reactive diluent G with epoxy groups. Such reactive diluents are known to the person skilled in the art. Preferred examples of reactive diluents with epoxy groups are:

[0112] - monofunctional, saturated or unsaturated, branched or unbranched, cyclic or acyclic C4-Ci8 alcohols, such as butanol glycidyl ether, hexanol glycidyl ether, 2-ethylhexanol glycidyl ether, allyl glycidyl ether, tetrahydrofurfuryl and furfuryl glycidyl ether, trimethoxysilyl glycidyl ether and the like; 30 - difunctional, saturated or unsaturated, branched or unbranched, cyclic or acyclic C2-Ci8 alcohols, such as ethylene glycol glycidyl ether, butylene glycol glycidyl ether, hexanediol glycidyl ether, octanediol glycidyl ether, cyclohexanedimethanol diglycidyl ether, neopentyl glycol diglycidyl ether and the like;

[0113] - monofunctional, saturated or unsaturated, branched or unbranched, cyclic or acyclic C4-Ci8 alcohols, such as butanol glycidyl ether, hexanol glycidyl ether, 2-ethylhexanol glycidyl ether, allyl glycidyl ether, tetrahydrofurfuryl and furfuryl glycidyl ether, trimethoxysilyl glycidyl ether and the like; 30 - difunctional, saturated or unsaturated, branched or unbranched, cyclic or acyclic C2-Ci8 alcohols, such as ethylene glycol glycidyl ether, butylene glycol glycidyl ether, hexanediol glycidyl ether, octanediol glycidyl ether, cyclohexanedimethanol diglycidyl ether, neopentyl glycol diglycidyl ether and the like;

[0114] - monofunctional, saturated or unsaturated, branched or unbranched, cyclic or acyclic C4-Ci8 alcohols, such as butanol glycidyl ether, hexanol glycidyl ether, 2-ethylhexanol glycidyl ether, allyl glycidyl ether, tetrahydrofurfuryl and furfuryl glycidyl ether, trimethoxysilyl glycidyl ether and the like;

[0115] - monofunctional, saturated or unsaturated, branched or unbranched, cyclic or acyclic C4-Ci8 alcohols, such as butanol glycidyl ether, hexanol glycidyl ether, 2-ethylhexanol glycidyl ether, allyl glycidyl ether, tetrahydrofurfuryl and furfuryl glycidyl ether, trimethoxysilyl glycidyl ether and the like;

[0116] - monofunctional, saturated or unsaturated, branched or unbranched, cyclic or acyclic C4-Ci8 alcohols, such as butanol glycidyl ether, hexanol glycidyl ether, 2-ethylhexanol glycidyl ether, allyl glycidyl ether, tetrahydrofurfuryl and furfuryl glycidyl ether, trimethoxysilyl glycidyl ether and the like;

[0117] - epoxidized mono- or dicarboxylic acids, such as glycidyl neodecanoate, glycidyl methacrylate, glycidyl benzoate, diglycidyl phthalate, diglycidyl tetrahydrophthalate and diglycidyl hexahydrophthalate, diglycidyl esters of dimer fatty acids and the like;

[0118] - epoxidized di- or tri-functional, low to high molecular weight polyether polyols, such as polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether and the like.

[0119] Particularly preferred are hexanediol diglycidyl ether, cresyl glycidyl ether, p-tert-butylphenyl glycidyl ether, polypropylene glycol diglycidyl ether and polyethylene glycol diglycidyl ether.

[0120] Advantageously, the total proportion of the reactive diluents G with epoxy groups is 0.1 to 15% by weight, preferably 0.1 to 5% by weight, particularly preferably 0.1 to 2% by weight, more preferably 0.2 to 1% by weight, based on the total weight of the thermosetting one-component epoxy resin composition.

[0121] The composition can comprise further ingredients, in particular catalysts, stabilizers, in particular thermal and / or light stabilizers, thixotropic agents, plasticizers, solvents, mineral or organic fillers, blowing agents, dyes and pigments, anticorrosives, surfactants, antifoams and adhesion promoters.

[0122] Suitable plasticizers are in particular phenol alkyl sulfonates or N-butylbenzamide, such as commercially available as Mesamoll® or Dellatol BBS from Bayer.

[0123] Suitable stabilizers are in particular optionally substituted phenols such as BHT or Wingstay® T (Elkem), sterically hindered amines or N-oxyl compounds such as TEMPO (Evonik).

[0124] Particularly preferred one-component epoxy resin compositions comprise:

[0125] - 10 to 60% by weight, in particular 30 to 60% by weight, based on the total weight of the epoxy resin composition, of an epoxy resin A having an average of more than one epoxy group per molecule; preferably 50 to 100% by weight, in particular 80 to 100% by weight, of the epoxy resin A is a liquid epoxy resin and 0 to 30% by weight, in particular 0 to 20% by weight, of the epoxy resin A is a solid epoxy resin;

[0126] - at least one epoxy resin curing agent B, wherein the curing agent B is a dihydrazide, preferably selected from the group consisting of aromatic dicarboxylic acid dihydrazides B1, preferably isophthalic acid dihydrazide, and aliphatic dicarboxylic acid dihydrazides B2, preferably adipic acid dihydrazide;

[0127] - at least one accelerator C for the at least one curing agent B, which is an imidazole of the formula (V) salt:

[0128]

[0129] wherein

[0130] R1is an organic radical having 1 to 20 C atoms,

[0131] R2, R3, R4and R5are each a H atom or an organic radical having 1 to 20 C atoms,

[0132] X is an anion, and

[0133] n is 1, 2 or 3, preferably 1 ;

[0134] Preferably, the imidazole of the formula (V) the salt is selected from the group consisting of 1 -ethyl-3-methylimidazolium ethylsulfate, 1 -ethyl-3-methylimidazolium diethylphosphate, 1 -butyl-3-methylimidazolium and 1 -ethyl-3-methylimidazolium acetate, most preferably 1 -ethyl-3-methylimidazolium ethylsulfate;

[0135] - preferably 15 to 45 wt.-%, in particular 20 to 40 wt.-%, based on the total weight of the thermosetting one-component epoxy resin composition, of at least one toughness improver D selected from the group consisting of end-capped polyurethane polymers D1, liquid rubbers D2 and core-shell polymers D3, preferably end-capped polyurethane polymers D1 ;

[0136] - preferably 5 to 40 wt.-%, preferably 10 to 30 wt.-%, based on the total weight of the thermosetting one-component epoxy resin composition, of a filler F selected from the group consisting of calcium carbonate, calcium oxide and fumed silica;

[0137] - preferably 0.1 to 15 wt.-%, preferably 0.1 to 5 wt.-%, particularly preferably 0.1 to 2 wt.-%, more preferably 0.2 to 1 wt.-%, based on the total weight of the thermosetting one-component epoxy resin composition, of a reactive diluent G carrying an epoxy group.

[0138] the imidazole of the formula (V) the anion X of the salt is selected from the group consisting of alkylsulfates; halides, more particularly chlorides; carboxylates; phosphates, more particularly dimethylphosphates; most preferably alkylsulfonates.

[0139] In formula (V), R1is a methyl group and R3is an ethyl group, or R1is a methyl group and R3is a butyl group, preferably R1is a methyl group and R3is an ethyl group. In both cases, R2, R4and R5are each H atoms and n is 1.

[0140] The molar ratio (B / C) of the at least one epoxy resin curing agent B to the at least one accelerator C is 6 - 120, preferably 10 - 100, more preferably 12 - 75.

[0141] The at least one accelerator C is present in the one-component thermosetting epoxy resin composition in an amount of 5 - 95 mmol / mol, preferably 10 - 50 mmol / mol, more preferably 15 - 25 mmol / mol of accelerator C to epoxy resin A.

[0142] The at least one curing agent B is present in the thermosetting epoxy resin composition in a molar ratio of 300 - 550 mmol / mol, preferably 400 - 500 mmol / mol, more preferably 425 - 475 mmol / mol of curing agent B to epoxy resin A.

[0143] It can also be advantageous when the preferred one-component epoxy resin composition consists of the above-mentioned ingredients to an extent of more than 80 wt.-%, preferably more than 90 wt.-%, in particular more than 95 wt.-%, particularly preferably more than 98 wt.-%, most preferably more than 99 wt.-%, based on the total weight of the epoxy resin composition.

[0144] It is advantageous when the epoxy resin composition of the present application has a viscosity at 25 °C, in particular measured using a rheometer in oscillation using a plate-plate geometry with the following parameters: 5 Hz, measurement gap 1 mm, plate-plate diameter 25 mm, 1 % deformation, of 500 - 4500 Pa*s, in particular 1000 - 3000 Pa*s, preferably 1500 - 2500 Pa*s. This is advantageous because this ensures a good applicability.

[0145] It has been found that the described thermosetting one-component epoxy resin composition is particularly suitable for use as a one-component thermosetting adhesive, in particular as a thermosetting one-component body adhesive in the construction of motor vehicles. Such one-component adhesives have a range of possible uses. They are required for the joining of thermally stable materials. Thermally stable materials are understood to mean materials which are dimensionally stable at least during the curing time at a curing temperature of 100 to 220°C, preferably 120 to 200°C. In particular, these are metals and plastics, such as ABS, polyamide, polyphenylene ether, composite materials, such as SMC, unsaturated polyester GFP, epoxy or acrylate composites. Preferred uses are those in which at least one of the materials is a metal. Considered particularly preferred uses are the joining of identical or different metals, in particular in the body construction in the automotive industry. Preferred metals are in particular steel, in particular electrogalvanized steel, hot-dip galvanized steel or oiled steel, Bonazinc-coated steel, and post-phosphated steel, and also aluminum, in particular in the variants which are generally encountered in automotive construction.

[0146] A further aspect of the present application relates to a method of joining thermally stable substrates comprising the following stages:

[0147] i) applying the thermosetting one-component epoxy resin composition as described in detail above to the surface of a thermally stable substrate S1, in particular a metal;

[0148] ii) bringing the applied thermosetting one-component epoxy resin composition into contact with the surface of a further thermally stable substrate S2, in particular a metal;

[0149] iii) heating the composition to a temperature of 100 to 220°C, in particular 120 to 200°C, preferably 130 to 150°C, more preferably 130 to 140°C.

[0150] Substrate S2 here consists of the same material as substrate S1 or a different material from substrate S1. Substrates S1 and / or S2 are in particular the metals and plastics mentioned above.

[0151] Preferably, in step iii), the composition is heated to a temperature of 100 to 220°C, in particular 120 to 200°C, preferably 130 to 150°C, more preferably 130 to 140°C, and the composition is held at the above-mentioned temperature for 10 min to 6 h, 10 min to 2 h, 10 min to 60 min, 10 min to 30 min, 10 min to 20 min, more preferably 10 min to 15 min.

[0152] Such a method of joining thermally stable materials results in an adhesive-bonded article. Such an article is preferably a vehicle or a component of a vehicle.

[0153] Further aspects of the present application thus relate to the adhesive-bonded articles obtained from the above-mentioned processes. Moreover, the compositions according to the present application are suitable not only for the automotive construction but also for the field of other applications. Relevant applications should be mentioned in particular in the construction of means of transport, such as ships, trucks, buses or rail vehicles, or in the construction of consumer goods, such as washing machines.

[0154] The materials which are adhesive-bonded by means of the compositions according to the present application are used at temperatures of generally 120 °C to -40 °C, preferably 100 °C to -40 °C, in particular 80 °C to -40 °C.

[0155] A particularly preferred use of the thermosetting one-component epoxy resin compositions of the present application is their use as thermosetting one-component body adhesives or reinforcement compounds in the construction of motor vehicles or as foamable, thermosetting compositions for the reinforcement of voids in structural parts and reinforcing elements.

[0156] A further aspect of the present application relates to the cured epoxy resin compositions as obtained by heating the thermosetting one-component epoxy resin compositions as described in detail above.

[0157] It has been found that the accelerators C of the present application as already described in detail above are suitable for combination with the curing agents B of the present application as accelerators for thermosetting epoxy resin compositions at curing temperatures of in particular 130 to 150 °C as components of thermosetting epoxy resin compositions.

[0158] More preferably, the compositions of the present application have the following properties:

[0159] After curing at 140 °C for 10 minutes:

[0160] - an LSS of > 27.5 MPa, in particular > 28 MPa, in particular > 28.5 MPa, in particular > 29 MPa, more preferably > 30 MPa, as measured as described in the experiments;

[0161] - an IP of > 29 N / mm, in particular > 30 N / mm, in particular > 31 N / mm, more preferably > 32 N / mm, as measured as described in the experiments.

[0162] Examples

[0163] In the following, some examples are cited which further illustrate the present application but are not intended to limit the scope of the present application in any way.

[0164] Preparation of the toughness improver ("D-1 ")

[0165] 150 g of poly-THF 2000 (OH number 57 mg / g KOH) and 150 of Liquiflex H (OH number 46 mg / g KOH) were dried at 105 °C under vacuum for 30 min. Once the temperature had been reduced to 90 °C, 61.5 g of IPDI and 0.14 g of dibutyltin dilaurate were added. The reaction was carried out at 90 °C under vacuum until the NCO content was constant after 2.0 h at 3.10 % (calculated NCO content: 3.15 %). Subsequently, 96.1 g of cardanol were added as blocking agent. Stirring was continued at 105 °C under vacuum until no more free NCO could be detected. The product was used as toughness improver D-1 as such.

[0166]

[0167] Raw materials used.

[0168] Production of the compositions

[0169] The reference compositions R1 -R12 and inventive compositions E1 to E12 were produced according to the compositions in Tables 2-4. The amounts stated in Tables 2-4 are in parts by weight.

[0170] The molar ratio (B / C) of the at least one epoxy resin curing agent B to the at least one accelerator C is shown in Tables 2-4 as "MR (B / C)".

[0171] Test methods:

[0172] Lap shear strength (LSS) (DIN EN 1465)

[0173] Clean test specimens (thickness 1.2 mm) of Elo H420 steel, which had been re-oiled (3 g / m 2 ) with Anticorit PL 3802-39S were bonded with the adhesives using glass beads as spacers at a bonding area of 25 x 10 mm at a layer thickness of 0.3 mm and cured at a target temperature of 140 °C for 10 min.

[0174] The lap shear strength was determined in triplicate according to DIN EN 1465 on a tensile tester at a strain rate of 10 mm / min.

[0175] Impact peel strength (IP RT) (according to ISO 11343)

[0176] Clean test specimens (thickness 1.2 mm) of Elo H420 steel, which had been re-oiled (3 g / m 2The samples were produced on a DC04+ZE steel with dimensions of 90 x 20 x 0.8 mm. The bonding area here was 20 x 30 mm, using glass beads as spacers with a layer thickness of 0.3 mm. The samples were cured at a target temperature of 140 °C for 10 minutes. The impact peel strength was measured on a Zwick 450 impact pendulum as a triple determination at 23 °C. The impact peel strength reported is the average force in N / mm from 25% to 90% of the measurement curve according to ISO 11343.

[0177] Viscosity / storage stability of the adhesive

[0178] To evaluate the storage stability of the adhesives, the viscosity measurement was repeated after 1 week of storage at 50 °C and the percentage of the viscosity increase produced after storage was determined. The increase in viscosity in % is shown in Tables 3 and 4 under "Visco increase" in percent. All compositions had a viscosity of 1500-2500 Pa*s at the start of the viscosity measurement. The viscosity was determined by rheometer in oscillation using a plate-plate geometry with the following parameters: 5 Hz, measurement gap 1 mm, plate-plate diameter 25 mm, 1% deformation.

[0179]

[0180] Table 2, n.c. = not cured

[0181]

[0182] Table 3, n.d. = not determined

[0183]

[0184] Table 4, n.d. = not determined.

Claims

1. Thermosettable one-component epoxy resin composition, comprising: a) at least one epoxy resin A having an average of more than one epoxy group per molecule; b) at least one epoxy resin curing agent B, wherein the curing agent B is a dihydrazide, preferably selected from aromatic dicarboxylic acid dihydrazides B1 and aliphatic dicarboxylic acid dihydrazides B2; and c) at least one accelerator C for the at least one curing agent B, which is an imidazole of formula (V) salt: wherein R1 is an organic group having 1 to 20 C atoms, R2, R3, R4 and R5 are each a H atom or an organic group having 1 to 20 C atoms, X is an anion, and n is 1, 2 or 3, preferably 1 ; Preferably, the imidazole of formula (V) the salt is selected from 1-ethyl-3-methylimidazolium the ethyl sulfate, 1-ethyl-3-methylimidazolium the diethyl phosphate, 1-butyl-3-methylimidazolium chloride and 1-ethyl-3-methylimidazolium the acetate, most preferably 1-ethyl-3-methylimidazolium the ethyl sulfate, wherein the molar ratio (B / C) of the at least one epoxy resin curing agent B to the at least one accelerator C is 6 - 120, preferably 10 - 100, more preferably 12 - 75.

2. The thermosetting one-part epoxy resin composition according to claim 1, characterized in that the curing agent B is an aromatic dicarboxylic acid dihydrazide B1, preferably selected from isophthalic acid dihydrazide and / or terephthalic acid dihydrazide, preferably isophthalic acid dihydrazide.

3. The thermosetting one-component epoxy resin composition according to any of the preceding claims, characterized in that the curing agent B is an aliphatic dicarboxylic acid dihydrazide B2, preferably selected from glutaric acid dihydrazide, adipic acid dihydrazide, pimelic acid dihydrazide, 8,12- eicosadienoic acid 1,20-dihydrazide and 4-isopropyl-2,5-dioxoimidazolidine-1,3-di(propanehydrazide), in particular adipic acid dihydrazide.

4. The thermosetting one-component epoxy resin composition according to any of the preceding claims, characterized in that imidazoles of formula (V) The anion X of the salt is selected from the group consisting of alkylsulfates; alkylsulfonates; halides, more particularly chloride, bromide and iodide; thiocyanates; dicyanamides; carboxylates; phosphates, more particularly dimethylphosphates and diethylphosphates; and phosphonates; preferably from the group consisting of alkylsulfates; halides, more particularly chloride; carboxylates; phosphates, more particularly dimethylphosphates; most preferably alkylsulfonates.

5. The thermosetting one-component epoxy resin composition according to any of the preceding claims, characterized in that in formula (V) R1 is a methyl group and R3 is an ethyl group, or R1 is a methyl group and R3 is a butyl group, preferably R1 is a methyl group and R3 is an ethyl group, and further characterized in that R2, R4 and R5 are each a H atom and n is 1.

6. The thermosetting one-component epoxy resin composition according to any of the preceding claims, characterized in that The molar ratio (B / C) of the at least one epoxy resin curing agent B to the at least one accelerator C is 12 - 25, preferably 14 - 20.

7. The thermosetting one-part epoxy resin composition according to any one of claims 1 to 5, characterized in that The molar ratio (B / C) of the at least one epoxy resin curing agent B to the at least one accelerator C is 25 - 75, preferably 26 - 70, more preferably 40 - 70.

8. The thermosetting one-component epoxy resin composition according to any of the preceding claims, characterized in that The at least one accelerator C is present in the one-component thermosettable epoxy resin composition in an amount of 5 - 95 mmol per mol of epoxy resin A, preferably 10 - 50 mmol per mol of epoxy resin A, more preferably 15 - 25 mmol per mol of epoxy resin A, in a molar ratio of accelerator C to epoxy resin A.

9. The thermosetting one-component epoxy resin composition according to any of the preceding claims, characterized in that The at least one curing agent B is present in the thermosettable epoxy resin composition in an amount of 300 - 550 mmol per mol of epoxy resin A, preferably 400 - 500 mmol per mol of epoxy resin A, more preferably 425 - 475 mmol per mol of epoxy resin A, in a molar ratio of curing agent B to epoxy resin A.

10. The thermosetting one-component epoxy resin composition according to any of the preceding claims, characterized in that The thermosettable epoxy resin composition additionally comprises at least one toughness improver D selected from the group consisting of end-capped polyurethane polymers D1, liquid rubbers D2 and core-shell polymers D3, preferably end-capped polyurethane polymers D1.

11. The thermosetting one-component epoxy resin composition according to any of the preceding claims, characterized in that The proportion of the epoxy resin A is 10 - 60 wt.-%, preferably 30 - 60 wt.-%, more preferably 40 - 55 wt.-%, based on the total weight of the one-component epoxy resin composition.

12. The thermosetting one-component epoxy resin composition according to any of the preceding claims, characterized in that The epoxy resin composition has a viscosity at 25 °C of 500 - 4500 Pa*s, in particular 1000 - 3000 Pa*s, preferably 1500 - 2500 Pa*s, preferably measured using a rheometer in oscillation using a plate-plate geometry with the following parameters: 5 Hz, measurement gap 1 mm, plate-plate diameter 25 mm, 1 % deformation.

13. Use of the thermosetting one-component epoxy resin composition according to any one of claims 1 to 12 as one-component thermosetting adhesive, in particular as thermosetting one-component body adhesive in the construction of motor vehicles.

14. Method for adhesive joining of thermally stable substrates comprising the following stages: i) application of the thermosetting one-component epoxy resin composition according to any one of claims 1 to 12 to the surface of a thermally stable substrate S1, in particular metal; ii) contacting the applied thermosetting one-component epoxy resin composition with the surface of a further thermally stable substrate S2, in particular metal; iii) heating the composition to a temperature of 100-220°C, in particular 120-200°C, preferably 130 to 150°C, more preferably 130 to 140°C; wherein the substrate S2 consists of the same material as the substrate S1 or a different material than the substrate S1.

15. The method according to claim 14, wherein in the step iii) of heating the composition to a temperature of 100-220°C, in particular 120-200°C, preferably 130 to 150°C, more preferably 130 to 140°C, the composition is kept at the above-mentioned temperature for 10 min - 6 h, 10 min - 2 h, 10 min - 60 min, 10 min - 30 min, 10 min - 20 min, more preferably 10 min - 15 min.

16. Adhesive joined article, obtained from the method according to any one of claims 14 to 15.

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