Storage stable epoxy resin composition

Abstract

The present invention relates to the use of boronic acids to enhance the storage stability of epoxy resin compositions and to epoxy resin compositions comprising an epoxy resin and a hardener and a boronic acid.

Description

[Technical field]

[0001] The present invention relates to the use of boronic acids to enhance the storage stability of epoxy resin compositions and to epoxy resin compositions comprising an epoxy resin and a hardener and a boronic acid. [Background technology]

[0002] The use of epoxy resins is widespread due to their excellent chemical resistance, their very good thermal and dynamic mechanical properties, and their high electrical insulating capacity. These epoxy resins are available in liquid or solid form and can be cured under the application of heat, with or without the addition of a hardener.

[0003] The curing of epoxy resins proceeds according to different mechanisms. In addition to curing with phenols or anhydrides, curing with amines is often carried out. These substances are usually liquid and can be mixed very well with epoxy resins. Due to the high reactivity, such epoxy resin compositions are carried out using two components. This means that the resin (component A) and the hardener (component B) are stored separately and mixed in the correct ratio just before use. These two-component resin formulations are also called cold-curing resin formulations, whereby the hardeners used in these are usually selected from the group of amines or amidoamines.

[0004] Single-component heat-curing epoxy resin formulations, on the other hand, are ready to use and pre-assembled, i.e. the epoxy resin and the hardener are mixed in the factory. Mixing errors of the individual components during local use are therefore excluded. A prerequisite for this is a latent curing system that does not react with the epoxy resin at room temperature, but reacts easily when heated, depending on the application of energy. In this context, "latent" means that the mixture of the individual components is stable under defined storage conditions.

[0005] For such single-component epoxy resin formulations, for example, dicyandiamide is a particularly suitable and also cost-effective hardener. Under ambient conditions, the corresponding epoxy resin-dicyandiamide mixtures can be stored ready-to-use for up to 12 months.

[0006] In order to lower the reaction temperature for curing single-component epoxy resin formulations such as epoxy resin-dicyandiamide mixtures, curing accelerators are generally added to these formulations to lower the activation energy for curing so that curing at lower temperatures is possible. However, these curing accelerators often reduce the storage stability of the epoxy resin composition containing the epoxy resin, the curing agent, and the curing accelerator, so that long-term storage at room temperature is not possible. Nevertheless, to ensure adequate storage stability of these single-component epoxy resin formulations, they must be stored at controlled low temperatures, often at -18°C. When less latent curing agents are used in epoxy resins, similar storage conditions must be maintained. This results in significant additional costs and labor for the storage, transportation and processing of the formulations, especially for the manufacture of prepregs, towpregs or adhesives.

[0007] Knowing such obstacles, proposals to overcome them have already been published. For example, European Patent Specification EP 659793 B1 describes a mixture of boric acid or borates (boric acid esters) and an imidazole-epoxy resin adduct as a hardener for epoxy resins. The compositions thus obtained are stable in storage and allow rapid curing by heating.

[0008] Furthermore, European patent specification EP 2678369 B1 describes liquid hardeners containing cyanamide, at least one urea derivative (uron) and at least one organic or inorganic acid as stabilizer. These hardeners are excellently soluble in epoxy resins, show high latency in epoxy resins and allow long-term storage stability.

[0009] Furthermore, it is known from European patent specification EP 2780388 B1 that N,N'-dimethyluron is capable of curing epoxy resins as the sole curing agent without the addition of a curing accelerator.

[0010] Furthermore, European Patent Application EP 3257884 A1 describes an epoxy resin mixture of epoxy resin, dicyandiamide, aromatic uron and boric acid ester. The effect of the boric acid esters listed in the examples, especially the extension of the time to the peak in the heat flow curve at 60°C, is very low, so it is doubtful whether the addition of these esters can eliminate the need for frozen storage and frozen transportation.

[0011] Furthermore, German patent application DE 10 2019 121 195.6 describes an epoxy resin composition comprising a hardener, a curing accelerator and a boronic acid for stabilizing the epoxy resin composition. Summary of the Invention

[0012] Accordingly, the present invention is directed to providing an epoxy resin composition containing a curing agent that can be stored for a substantial period of time, up to several days, without any observable cure, and that should have high latency, i.e., high storage stability, below the cure temperature, as well as high reactivity at the cure temperature.

[0013] These problems may be solved by the use according to claim 1 as well as by the epoxy resin composition according to claim 6. Preferred embodiments of the invention are given in the subclaims which may be combined in any way with one another. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] That is, according to a first embodiment, the subject of the present invention is the use of a boronic acid of general formula (I) for increasing the storage stability of an epoxy resin composition, in particular a liquid epoxy resin composition, comprising an epoxy resin, in particular a liquid epoxy resin, and a curing agent for curing said epoxy resin, wherein formula (I) is

[0015] [ka]

[0016] (Wherein, radical R 1 teeth: R 1 = alkyl, hydroxyalkyl or a radical of formula (II) wherein formula (II) means

[0017] [ka]

[0018] (In the formula, R 2 , R 3 , R 4 are independent of each other, R 2 , R 3 , R 4 = Hydrogen, fluorine, chlorine, bromine, iodine, cyano, C1 to C5 alkyl, alkoxy, acyl, alkylsulfonyl, aryl, carboxyl, or B(OH)2 and at least one radical R 2 , R 3 , R 4 represents a group that is not hydrogen, The epoxy resin composition comprises as a curing agent a curing agent according to formula (III), where formula (III) is:

[0019] [ka]

[0020] (In the formula, R 6 , R7 , R 8 are independent of each other: R 6 , R 7 = independently of each other hydrogen or C1 to C5 alkyl, R 8 =-NHC(O)NR 6 R 7 C1 to C replaced with 15 Alkyl, -NHC(O)NR 6 R 7 C3 to C replaced with 15 Cycloalkyl, -NHC(O)NR 6 R 7 or -NHC(O)NR 6 R 7 Alkylaryl substituted with ), The epoxy resin composition does not contain, in addition to the curing agent according to general formula (III), a curing agent selected from the group consisting of cyanamide, guanidine, cyanoguanidine, nitroguanidine, acylguanidine, biguanidine and a curing agent according to general formula (IV), where formula (IV) is as follows:

[0021] [ka]

[0022] (Wherein, radical R 40 , R 41 , R 42 are independent of each other: R 40 = cyano, nitro, acyl or formula -(C=X)-R 43 (In the formula, X=imino or oxygen, R 43 = amino, alkylamino or alkoxy) The radical of R 41 = hydrogen, C1 to C5 alkyl, aryl, benzyl, or acyl; R42 = Hydrogen or C1 to C5 alkyl means).

[0023] Particularly preferably, the epoxy resin composition does not contain any further curing agent, co-curing agent, curing accelerator or other catalyst for curing the epoxy resin in addition to the curing agent of general formula (III).

[0024] That is, according to a further embodiment, the subject of the present invention is the use of a boronic acid of general formula (I) for increasing the storage stability of an epoxy resin composition, in particular a liquid epoxy resin composition, comprising an epoxy resin, in particular a liquid epoxy resin, and a curing agent for curing said epoxy resin, wherein formula (I) is

[0025] [ka]

[0026] (Wherein, radical R 1 teeth: R 1 = alkyl, hydroxyalkyl or a radical of formula (II) wherein formula (II) means

[0027] [ka]

[0028] (In the formula, R 2 , R 3 , R 4 are independent of each other, R 2 , R 3 , R 4 = Hydrogen, fluorine, chlorine, bromine, iodine, cyano, C1 to C5 alkyl, alkoxy, acyl, alkylsulfonyl, aryl, carboxyl, or B(OH)2 and at least one radical R 2 , R 3 , R 4 represents a group that is not hydrogen, The epoxy resin composition comprises as a curing agent a curing agent according to formula (III), where formula (III) is:

[0029] [ka]

[0030] (In the formula, R 6 , R 7 , R 8 are independent of each other, R 6 , R 7 = independently of each other hydrogen or C1 to C5 alkyl, R 8 =-NHC(O)NR 6 R 7 C1 to C replaced with 15 Alkyl, -NHC(O)NR 6 R 7 C3 to C replaced with 15 Cycloalkyl, -NHC(O)NR 6 R 7 or -NHC(O)NR 6 R 7 Alkylaryl substituted with ), The epoxy resin composition does not contain, in addition to the curing agent of general formula (III), any further curing agent, co-curing agent, curing accelerator or other catalyst for curing the epoxy resin.

[0031] Surprisingly, it has been shown that the addition of a boronic acid according to formula (I) of the present invention to an epoxy resin composition containing an epoxy resin, a curing agent according to formula (III), significantly improves the storage stability of the epoxy resin composition already prepared in that way for curing. For example, the latency of a TDI-uron-containing epoxy resin composition can be increased by 6 to 12 times by adding a boronic acid according to the present invention (see examples), so that the corresponding epoxy resin composition can be stored at room temperature up to 40° C. for at least 2 months longer, i.e., can be stored without curing, compared to an otherwise identical composition without the addition of a boronic acid according to the present invention. Quite surprisingly, it has been shown that the desired storage stability is achieved without significantly changing the reactivity of the composition. The addition of a boronic acid does not affect the glass transition temperature achieved or the mechanical properties of the fiber-reinforced composite material. That is, the overall curing properties of the curing agent and curing accelerator achieved without the addition of a boronic acid are not changed and are essentially maintained. These facts are surprising in their entirety. Overall, therefore, it is possible to provide an epoxy resin composition which exhibits high storage stability at room temperature and high reactivity at curing temperatures, and which is extremely suitable for use in prepregs, towpregs and one-component adhesives, as well as acoustic insulation materials.

[0032] According to the present invention, an epoxy resin composition means a composition in which the epoxy resins are thermosetting, i.e. polymerizable, linkable and / or crosslinkable by heat due to their functional groups, i.e. epoxy groups, where the polymerization, linkage and / or crosslinking occurs as a result of polyaddition induced by a curing agent.

[0033] In the context of the present invention, alkyl means a saturated, linear or branched aliphatic radical, in particular of the general formula C n H 2n+1 where n represents the number of carbon atoms of the radical. Alkyl can also mean a radical having a higher number of carbon atoms. Preferably, alkyl is a radical of the general formula C n H2n+1 where n represents the number of carbon atoms in the radical, n being a number from 1 to 15. That is, alkyl preferably has a carbon number ranging from C1 to C 15 Alkyl, more preferably C1 to C 10 It means alkyl, from C1 to C 15 It is further preferred that alkyl is in particular methyl, ethyl, n-propyl, 1-methylethyl, n-butyl, 1-methylpropyl, 2-methylpropyl, 1,1-dimethylethyl, n-pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, 2,2-dimethylpropyl, 1-ethylpropyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl or n-pentadecyl.

[0034] Furthermore, C1 to C5 alkyl denotes a saturated, linear or branched alkyl radical having up to 5 carbon atoms. Preferably, C1 to C5 alkyl denotes in particular methyl, ethyl, n-propyl, 1-methylethyl, n-butyl, 1-methylpropyl, 2-methylpropyl, 1,1-dimethylethyl, n-pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, 2,2-dimethylpropyl or 1-ethylpropyl.

[0035] According to the invention, hydroxyalkyl means an alkyl radical as defined above, which is substituted with one, two or three hydroxy groups. In particular, according to the invention, hydroxyalkyl means an alkyl radical having up to 15 carbon atoms and substituted with a hydroxy group. That is, hydroxyalkyl is preferably a C1 to C2 alkyl radical. 15More preferably, hydroxyalkyl means C1 to C5 hydroxyalkyl. Most preferably, hydroxyalkyl means hydroxymethyl, 2-hydroxyethyl, 3-hydroxypropyl, 4-hydroxybutyl or 5-hydroxypentyl.

[0036] In the context of the present invention, C3 to C 15 Cycloalkyl is a saturated monocyclic or bicyclic aliphatic radical having 3 to 15 carbon atoms, in particular of the general formula C n H 2n-1 where n=an integer from 3 to 15. In this context, C3 to C 15 Cycloalkyl is preferably intended to mean in particular cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl or cycloheptyl, where these cycloalkyl radicals can in turn be mono- or polysubstituted further by alkyl, preferably as defined above.

[0037] According to the present invention, C3 to C 15 Cycloalkyl particularly preferably denotes cyclopentyl, cyclohexyl, which in turn can be mono- or polysubstituted by alkyl, and especially 3,3,5,5-tetramethyl-1-cyclohexyl.

[0038] Cyano refers to a nitrile group of the general formula CN.

[0039] Nitro refers to a functional group of the general formula NO2.

[0040] Amino refers to a functional group of general formula NH2.

[0041] Imino refers to a functional group of the general formula NH.

[0042] Alkylamino has the formula NH n (Alkyl) 2-n(n=0 or 1), where alkyl is an alkyl radical as defined above and the attachment site is located on the nitrogen.

[0043] Carboxyl refers to a functional group of the general formula COOH.

[0044] Alkoxy means a radical of the formula O-alkyl, where alkyl is an alkyl radical as defined above and the attachment site is located on the oxygen. According to the invention, alkoxy means in particular an alkoxy radical whose alkyl radical has up to 15 carbon atoms, in particular up to 5 carbon atoms. That is to say, alkoxy is preferably a C1 to C6 alkyl radical. 15 Alkoxy is more preferably C1 to C5 alkoxy. Particularly preferably, alkoxy is methoxy, ethoxy, n-propoxy, n-butoxy or n-pentoxy.

[0045] Acyl is a group of the formula C(O)-R 5 where R 5 is bonded to carbon and hydrogen, alkyl or alkoxy can be as defined above, and the site of attachment of the acyl radical is located on the carbon. Particularly preferably, acyl denotes formyl or acetyl.

[0046] Moreover, alkylsulfonyl means a radical of the formula SO2-alkyl, where both the attachment site of the alkylsulfonyl radical and the alkyl radical are located on sulfur, and alkyl is an alkyl radical as defined above. According to the invention, alkylsulfonyl in particular means an alkylsulfonyl radical, the alkyl radical of which has up to 15 carbon atoms. That is to say, alkylsulfonyl is preferably a C1 to C2 alkyl radical. 15 Alkylsulfonyl is more preferably C1 to C5 alkylsulfonyl. Particularly preferred alkylsulfonyl is methylsulfonyl, ethylsulfonyl, n-propylsulfonyl, n-butylsulfonyl or n-pentylsulfonyl.

[0047] According to the invention, aryl means an aromatic radical, in particular an aromatic radical having 6 to 15 carbon atoms, which may be monocyclic, bicyclic or polycyclic. That is, aryl is preferably C6 to C 15 C6 to C monosubstituted with aryl, especially benzylphenyl, or then arylalkyl, especially arylmethyl, especially phenylmethyl 15 Particularly preferably, aryl denotes phenyl, naphthyl, anthryl, phenanthryl, pyrenyl or perylenyl, most preferably phenyl.

[0048] Furthermore, according to the invention, alkylaryl means an aromatic radical of the above type, which is then mono- or polysubstituted with alkyl of the above type. In particular, alkylaryl means an aromatic radical having 6 to 15 carbon atoms. That is, alkylaryl is preferably a C6 to C 15 More preferably, alkylaryl means methylphenyl, dimethylphenyl or trimethylphenyl.

[0049] According to the present invention, a boronic acid of formula (I) can be employed or used, where R 1 may mean alkyl, hydroxyalkyl or a radical of formula (II). Preferably, R in formula (I) 1 may be alkyl or hydroxyalkyl, where more preferably, R 1 It is provided that: R 1 = methyl, ethyl, n-propyl, 1-methylethyl, n-butyl, 1-methylpropyl, 2-methylpropyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decanyl, hydroxymethyl, 2-hydroxyethyl, 3-hydroxypropyl, 4-hydroxybutyl or 5-hydroxypentyl

[0050] According to the present invention, R1 also contains at least one substituent R 2 , R 3 , R 4 Alternatively, R in formula (I) may be a radical of formula (II) in which R is not hydrogen. 1 is preferably a radical R 2 , R 3 , R 4 but: R 2 = fluorine, chlorine, bromine, iodine, cyano, C1 to C5 alkyl, alkoxy, acyl, alkylsulfonyl, aryl, carboxyl or B(OH)2, R 3 , R 4 = Hydrogen It may mean a radical of formula (II) which means

[0051] More preferably, R 1 is the radical R 2 , R 3 , R 4 but: R 2 = fluorine, acyl, alkoxy or B(OH)2, R 3 , R 4 = Hydrogen It may be a radical of formula (II) which means

[0052] Even more preferably, R in formula (I) 1 is the radical R 2 , R 3 , R 4 but: R 2 = fluorine, formyl, acetyl, methoxy, ethoxy, n-propoxy, n-butoxy, n-pentoxy, or B(OH)2, R 3 , R 4 = Hydrogen It may be a radical of formula (II) which means

[0053] According to a further alternative, boronic acids according to formula (I) can also be preferably employed or used, where R 1 is preferably a radical R 2 , R 3 , R 4 but: R 2 , R 3 = independently of each other fluorine, chlorine, bromine, iodine, cyano, C1 to C5 alkyl, alkoxy, acyl, alkylsulfonyl, aryl, carboxyl or B(OH)2, R 4 = Hydrogen means a radical of formula (II)

[0054] More preferably, R 1 is the radical R 2 , R 3 , R 4 but: R 2 , R 3 = independently of each other fluorine, acyl, alkoxy or B(OH)2, R 4 = Hydrogen It may be a radical of formula (II) which means

[0055] Even more preferably, R in formula (I) 1 is the radical R 2 , R 3 , R 4 but: R 2 , R 3 = independently of one another fluorine, formyl, acetyl, methoxy, ethoxy, n-propoxy, n-butoxy, n-pentoxy- or B(OH)2, R 4 = Hydrogen It may be a radical of formula (II) which means

[0056] According to a further alternative, boronic acids according to formula (I) can be preferably used or employed, where R 1 is preferably a radical R 2 , R 3 , R 4 but independently of each other: R 2 , R 3 , R 4 = fluorine, chlorine, bromine, iodine, cyano, C1 to C5 alkyl, alkoxy, acyl, alkylsulfonyl, aryl, carboxyl or B(OH)2 means a radical of formula (II)

[0057] More preferably, R 1 is the radical R 2 , R 3 , R 4 but independently of each other: R 2 , R 3 , R 4 = Fluorine or C1 to C5 alkyl It may be a radical of formula (II) which means

[0058] Even more preferably, R in formula (I) 1 is the radical R 2 , R 3 , R 4 but independently of each other: R 2 , R 3 , R 4 = Fluorine, methyl, ethyl, n-propyl, 1-methylethyl, n-butyl, 1-methylpropyl, 2-methylpropyl, 1,1-dimethylethyl, n-pentyl It may be a radical of formula (II) which means

[0059] Very preferably, formula (I) represents a substance selected from the group consisting of 4-formylphenylboronic acid, 1,4-benzenediboronic acid, 3-fluorophenylboronic acid, 2,4-difluorophenylboronic acid, 2,5-dimethoxyphenylboronic acid, methylboronic acid, 4-ethylphenylboronic acid, 1-octylboronic acid, 2-carboxy-phenylboronic acid, 3-carboxyphenylboronic acid, 4-carboxyphenylboronic acid, (2-hydroxymethyl)phenylboronic acid, 4-cyanophenylboronic acid, 4-(methanesulfonyl)phenylboronic acid, 3,4,5-trifluorophenylboronic acid or mixtures thereof.

[0060] The use of these boronic acids in epoxy resin compositions can improve the storage stability of epoxy resin compositions already prepared for curing to an exceptionally high degree.

[0061] Highly preferably, the compound of formula (III) comprises all radicals R 6 and R 7 are used as hardeners in which the radicals R are identical, in particular methyl, ethyl, n-propyl, i-propyl, n-butyl or n-pentyl. 6 and two radicals R 7 are identical and the radical is selected from the group consisting of methyl, ethyl, n-propyl, i-propyl, n-butyl and n-pentyl. However, if the two radicals R 6 or two radicals R 7 Or all four radicals may also be different from each other, in which case the radicals are also preferably selected from the group consisting of methyl, ethyl, n-propyl, i-propyl, n-butyl or n-pentyl.

[0062] Thus, according to a further idea, an epoxy resin composition, in particular a liquid epoxy resin composition, comprising an epoxy resin, in particular a liquid epoxy resin, and a curing agent for curing said epoxy resin, and at least one boronic acid of general formula (I), in which formula (I) is:

[0063] [ka]

[0064] (Wherein, radical R 1 teeth: R 1 = alkyl, hydroxyalkyl or a radical of formula (II) wherein formula (II) means

[0065] [ka]

[0066] (In the formula, R 2 , R 3 , R 4 are independent of each other, R 2 , R 3 , R 4 = Hydrogen, fluorine, chlorine, bromine, iodine, cyano, C1 to C5 alkyl, alkoxy, acyl, alkylsulfonyl, aryl, carboxyl, or B(OH)2 and at least one radical R 2 , R 3 , R 4 represents a group that is not hydrogen, The epoxy resin composition comprises as a curing agent a curing agent according to formula (III), where formula (III) is:

[0067] [ka]

[0068] (In the formula, R 6 , R 7 , R 8 are independent of each other: R 6 , R 7 = independently of each other hydrogen or C1 to C5 alkyl, R 8 =-NHC(O)NR 6R 7 C1 to C replaced with 15 Alkyl, -NHC(O)NR 6 R 7 C3 to C replaced with 15 Cycloalkyl, -NHC(O)NR 6 R 7 or -NHC(O)NR 6 R 7 Alkylaryl substituted with ), The epoxy resin composition does not contain, in addition to the curing agent according to general formula (III), a curing agent selected from the group consisting of cyanamide, guanidine, cyanoguanidine, nitroguanidine, acylguanidine, biguanidine and a curing agent according to general formula (IV), where formula (IV) is as follows:

[0069] [ka]

[0070] (Wherein, radical R 40 , R 41 , R 42 are independent of each other: R 40 = cyano, nitro, acyl or formula -(C=X)-R 43 (In the formula, X=imino or oxygen, R 43 = amino, alkylamino or alkoxy) The radical of R 41 = hydrogen, C1 to C5 alkyl, aryl, benzyl, or acyl; R 42 = Hydrogen or C1 to C5 alkyl means.

[0071] Particularly preferably, also in this embodiment, the epoxy resin composition does not contain any further curing agent, co-curing agent, curing accelerator or other catalyst for curing the epoxy resin in addition to the curing agent of general formula (III).

[0072] That is, an epoxy resin composition, in particular a liquid epoxy resin composition, comprising an epoxy resin, in particular a liquid epoxy resin, and a curing agent for curing said epoxy resin, is also a subject of the present invention, in which the formula (I) is

[0073] [ka]

[0074] (Wherein, radical R 1 teeth: R 1 = alkyl, hydroxyalkyl or a radical of formula (II) wherein formula (II) means

[0075] [ka]

[0076] (In the formula, R 2 , R 3 , R 4 are independent of each other, R 2 , R 3 , R 4 = Hydrogen, fluorine, chlorine, bromine, iodine, cyano, C1 to C5 alkyl, alkoxy, acyl, alkylsulfonyl, aryl, carboxyl, or B(OH)2 and at least one radical R 2 , R 3 , R 4 represents a group that is not hydrogen, The epoxy resin composition comprises as a curing agent a curing agent according to formula (III), where formula (III) is:

[0077] [ka]

[0078] (In the formula, R 6 , R 7 , R 8 are independent of each other, R 6 , R 7 = independently of each other hydrogen or C1 to C5 alkyl, R 8 =-NHC(O)NR 6 R 7 C1 to C replaced with 15 Alkyl, -NHC(O)NR 6 R 7 C3 to C replaced with 15 Cycloalkyl, -NHC(O)NR 6 R 7 or -NHC(O)NR 6 R 7 Alkylaryl substituted with ), The epoxy resin composition does not contain, in addition to the curing agent of general formula (III), any further curing agent, co-curing agent, curing accelerator or other catalyst for curing the epoxy resin.

[0079] According to a further idea, it is also an object of the present invention to provide an epoxy resin composition, in particular a liquid epoxy resin composition, which consists of at least one epoxy resin, in particular at least one liquid epoxy resin, and a curing agent for curing said epoxy resin and at least one boronic acid of general formula (I), said curing agent consisting of at least one urea derivative according to formula (III).

[0080] Surprisingly, such epoxy resin compositions have been shown to be particularly stable on storage. That is, the epoxy resin compositions according to the invention have been shown to have significantly higher storage stability (see examples) compared to known epoxy resin compositions. The epoxy resin compositions according to the invention can be stored or have a longer storage stability under the same conditions, i.e. by at least a factor of 6 to 16, than comparable epoxy resin compositions without boronic acid. Very surprisingly, other curing properties, such as the reactivity of the compositions, have been shown to be comparable to the curing properties of known compositions and do not change significantly. That is, these compositions can be excellently used for the production of prepregs, towpregs and one-component adhesives as well as acoustic insulation materials.

[0081] The preferred embodiments of the above uses, in particular the preferred uses of the boronic acids, are also preferred embodiments of the epoxy resin composition of the present invention, i.e. the epoxy resin composition of the present invention preferably comprises a boronic acid according to formula (I), where R 1 Preferably, R in formula (I) is alkyl or hydroxyalkyl. More preferably, R 1 teeth: R 1 = methyl, ethyl, n-propyl, 1-methylethyl, n-butyl, 1-methylpropyl, 2-methylpropyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decanyl, hydroxymethyl, 2-hydroxyethyl, 3-hydroxypropyl, 4-hydroxybutyl or 5-hydroxypentyl It can mean:

[0082] According to the present invention, R 1 also contains at least one substituent R 2 , R 3 , R 4is not hydrogen. That is, the epoxy resin composition may alternatively and preferably comprise a boronic acid according to formula (I), where R 1 is the radical R 2 , R 3 , R 4 but: R 2 = fluorine, chlorine, bromine, iodine, cyano, C1 to C5 alkyl, alkoxy, acyl, alkylsulfonyl, aryl, carboxyl or B(OH)2, R 3 , R 4 = Hydrogen is a radical of formula (II)

[0083] More preferably, R 1 is R in formula (II) 2 , R 3 , R 4 but: R 2 = fluorine, acyl, alkoxy or B(OH)2, R 3 , R 4 = Hydrogen It may be a radical of formula (II) which means

[0084] Even more preferably, R in formula (I) 1 is R in formula (II) 2 , R 3 , R 4 but: R 2 = fluorine, formyl, acetyl, methoxy, ethoxy, n-propoxy, n-butoxy, n-pentoxy or B(OH)2, R 3 , R 4 = Hydrogen It may be a radical of formula (II) which means

[0085] According to a further alternative, the epoxy resin composition may also preferably comprise a boronic acid according to formula (I), where R 1 is the radical R 2 , R3 , R 4 but: R 2 , R 3 = independently of each other fluorine, chlorine, bromine, iodine, cyano, C1 to C5 alkyl, alkoxy, acyl, alkylsulfonyl, aryl, carboxyl or B(OH)2, R 4 = Hydrogen is a radical of formula (II)

[0086] More preferably, R 1 is R in formula (II) 2 , R 3 , R 4 but: R 2 , R 3 = independently of each other fluorine, acyl, alkoxy or B(OH)2, R 4 = Hydrogen It may be a radical of formula (II) which means

[0087] Even more preferably, R in formula (I) 1 is R in formula (II) 2 , R 3 , R 4 but: R 2 , R 3 = independently of one another fluorine, formyl, acetyl, methoxy, ethoxy, n-propoxy, n-butoxy, n-pentoxy or B(OH)2, R 4 = Hydrogen It may be a radical of formula (II) which means

[0088] According to a further alternative, the epoxy resin composition may also preferably comprise a boronic acid according to formula (I), where R 1 is the radical R 2 , R 3 , R 4 but independently of each other: R 2 , R 3 , R 4= fluorine, chlorine, bromine, iodine, cyano, C1 to C5 alkyl, alkoxy, acyl, alkylsulfonyl, aryl, carboxyl or B(OH)2 is a radical of formula (II)

[0089] More preferably, R 1 is R in formula (II) 2 , R 3 , R 4 but independently of each other: R 2 , R 3 , R 4 = Fluorine or C1 to C5 alkyl It may be a radical of formula (II) which means

[0090] Even more preferably, R in formula (I) 1 is R in formula (II) 2 , R 3 , R 4 but independently of each other: R 2 , R 3 , R 4 = Fluorine, methyl, ethyl, n-propyl, 1-methylethyl, n-butyl, 1-methylpropyl, 2-methylpropyl, 1,1-dimethylethyl, n-pentyl It may be a radical of formula (II) which means

[0091] Most preferably, the epoxy resin composition may comprise a boronic acid selected from the group consisting of 4-formylphenylboronic acid, 1,4-benzenediboronic acid, 3-fluorophenylboronic acid, 2,4-difluorophenylboronic acid, 2,5-dimethoxyphenylboronic acid, methylboronic acid, 4-ethylphenylboronic acid, 1-octylboronic acid, 2-carboxyphenylboronic acid, 3-carboxyphenylboronic acid, 4-carboxyphenylboronic acid, (2-hydroxymethyl)phenylboronic acid, 4-cyanophenylboronic acid, 4-(methanesulfonyl)phenylboronic acid, 3,4,5-trifluorophenylboronic acid, or mixtures thereof.

[0092] According to the present invention, a urea derivative according to formula (III) is used or employed as a curing agent for curing epoxy resins, where formula (III) is

[0093] [ka]

[0094] (In the formula, R 6 , R 7 , R 8 are independent of each other: R 6 , R 7 = independently of each other hydrogen or C1 to C5 alkyl, R 8 =-NHC(O)NR 6 R 7 C1 to C replaced with 15 Alkyl, -NHC(O)NR 6 R 7 C3 to C replaced with 15 Cycloalkyl, -NHC(O)NR 6 R 7 or -NHC(O)NR 6 R 7 Alkylaryl substituted with (meaning).

[0095] Due to their properties, these urea derivatives may be particularly well used for the gentle curing of epoxy resins and epoxy resin compositions.

[0096] Among the urea derivatives described by formula (III), aromatic urea derivatives can preferably be employed or used according to the invention. Further preferred are those having the radical R 6 , R 7 , R 8 But independently: R 6 , R 7= independently of each other C1 to C5 alkyl, in particular methyl or ethyl; R 8 =-NHC(O)NR 6 R 7 or -NHC(O)NR 6 R 7 Alkylaryl substituted with is an aromatic urea derivative of the formula (III)

[0097] More preferably, the radical R 6 , R 7 , R 8 are, independently of each other: R 6 , R 7 = independently of each other C1 to C5 alkyl, in particular methyl or ethyl; R 8 =-NHC(O)NRR 6 R 7 Alkylaryl substituted with It could be.

[0098] That is, according to the present invention, the urea derivative according to formula (V) represents a urea derivative according to formula (III), and the urea derivative according to formula (III) is particularly preferred. According to the present invention, the urea derivative according to formula (V) is:

[0099] [ka]

[0100] and the radical R 6 , R 7 , R 9 , R 10 but independently of each other: R 6 , R 7 = independently of each other hydrogen or C1 to C5 alkyl, in particular methyl or ethyl, R 9 , R 10 = independently of each other hydrogen or C1 to C5 alkyl, in particular hydrogen, methyl or ethyl Particularly preferred are urea derivatives according to formula (V)

[0101] Preferably, the radical R associated with formula (V) 6 , R 7 , R 9 respectively mean methyl radical, and R 10 means hydrogen. Particularly preferred are 1,1'-(4-methyl-m-phenylene)bis(3,3-dimethylurea) and 1,1'-(2-methyl-m-phenylene)bis(3,3-dimethylurea).

[0102] More preferably, the radical R 6 , R 7 , R 8 Independently: R 6 , R 7 = independently of each other C1 to C5 alkyl, in particular methyl or ethyl; R 8 =-NHC(O)NR 6 R 7 Aryl substituted with, especially -NHC(O)NR 6 R 7 Benzylphenyl substituted with It could be.

[0103] That is, according to the invention, the urea derivative according to formula (VII) represents a urea derivative according to formula (III), and the urea derivative according to formula (III) is particularly preferred.

[0104] [ka]

[0105] and the radical R 6 , R 7 , R 9 , R 10 but independently of each other: R 6 , R 7 = independently of each other hydrogen or C1 to C5 alkyl, in particular methyl or ethyl Particularly preferred are urea derivatives according to formula (VII)

[0106] Particularly preferred is the radical R 6 , R 7 Each denotes methyl. Very particularly preferred is 1,1'-(methylenedi-p-phenylene)bis[3,3-dimethylurea].

[0107] Among the urea derivatives described by formula (III), aliphatic urea derivatives can also be preferably used. 6 , R 7 , R 8 But independently: R 6 , R 7 = independently of each other hydrogen or C1 to C5 alkyl, in particular methyl or ethyl, R 8 =-NHC(O)NR 5 R 6 C1 to C replaced with 15 Alkyl or -NHC(O)NR 5 R 6 C3 to C replaced with 15 Cycloalkyl Further preferred are aliphatic urea derivatives of formula (III)

[0108] More preferably, R 6 and R 7 is as defined above, in particular methyl or ethyl, and R 3 -NHC(O)NR 1 R 2 C1 to C replaced with 15 The aliphatic urea derivative according to formula (III) is cycloalkyl.

[0109] That is, according to the present invention, a urea derivative according to formula (VI) means a urea derivative according to formula (III), and a urea derivative according to formula (III) is particularly preferred. According to the present invention, the urea derivative according to formula (VI) is:

[0110] [ka]

[0111] where the radicals may be simultaneously or independently of one another: R 6 , R 7 = independently of each other hydrogen or C1 to C5 alkyl, in particular methyl or ethyl; R 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 , R 20 = independently of each other hydrogen, C1 to C5 alkyl or -NHC(O)NR 6 R 7 C1 to C5 alkyl substituted with means, Radical R 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 or R 20 One of them is -NHC(O)NR 6 R 7 Particularly preferred are urea derivatives according to formula (VI), wherein R is C1 to C5 alkyl substituted with R.

[0112] More preferably, R 6 and R 7 are each independently methyl or ethyl, R 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 , R 20are each independently hydrogen, methyl, ethyl, -NHC(O)NR 6 R 7 or -NHC(O)NR 6 R 7 Particularly preferred is a curing agent comprising an aliphatic urea derivative of formula (VI) in which R is substituted methyl or ethyl. Particularly preferred is 1-(N,N-dimethylurea)-3-(N,N-dimethylurea-methyl)-3,5,5-trimethylcyclohexane (i.e., R is substituted methyl or ethyl) hereinafter also N'-[3-[[[(dimethylamino)carbonyl]amino]methyl]-3,5,5-trimethylcyclohexyl]-N,N-dimethylurea. 6 =R 7 =R 12 =R 13 =R 16 Methyl and R 17 =-CH2-NHC(O)N(CH3)2 and R 11 =R 14 =R 15 =R 18 =R 19 =R 20 = hydrogen).

[0113] Also preferred is an epoxy resin composition, in particular a liquid epoxy resin composition, comprising an epoxy resin, in particular a liquid epoxy resin, and a curing agent for curing said epoxy resin selected from the group of curing agents according to formula (V) or formula (VI) or formula (VII), and at least one boronic acid of general formula (I), wherein formula (I) is:

[0114] [ka]

[0115] (Wherein, radical R 1 teeth: R 1 = alkyl, hydroxyalkyl or a radical of formula (II) wherein formula (II) means

[0116] [ka]

[0117] (In the formula, R 2 , R 3 , R 4 are independent of each other, R 2 , R 3 , R 4 = Hydrogen, fluorine, chlorine, bromine, iodine, cyano, C1 to C5 alkyl, alkoxy, acyl, alkylsulfonyl, aryl, carboxyl, or B(OH)2 and at least one radical R 2 , R 3 , R 4 represents a group that is not hydrogen, Formula (V) is:

[0118] [ka]

[0119] represents the radical R 6 , R 7 , R 9 , R 10 are independent of each other: R 6 , R 7 = independently of each other hydrogen or C1 to C5 alkyl, in particular methyl or ethyl, R 9 , R 10 = independently of each other hydrogen or C1 to C5 alkyl, in particular hydrogen, methyl or ethyl means, Formula (VI) is

[0120] [ka]

[0121] in which the radicals may simultaneously or independently of one another be: R 6 , R7 = independently of each other hydrogen or C1 to C5 alkyl, in particular methyl or ethyl; R 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 , R 20 = independently of each other hydrogen, C1 to C5 alkyl, in particular methyl or ethyl, or -NHC(O)NR 6 R 7 C1 to C5 alkyl substituted with, in particular -NHC(O)NR 6 R 7 Methyl or ethyl substituted with means, Radical R 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 or R 20 One of them is -NHC(O)NR 6 R 7 and C1 to C5 alkyl substituted with Formula (VII) is

[0122] [ka]

[0123] and the radical R 6 , R 7 are independent of each other: R 6 , R 7 = independently of each other hydrogen or C1 to C5 alkyl, in particular methyl or ethyl means, The epoxy resin composition does not comprise, in addition to the curing agent of general formula (V) or formula (VI) or formula (VII), a curing agent selected from the group consisting of cyanamide, guanidine, cyanoguanidine, nitroguanidine, acylguanidine, biguanidine, and a curing agent according to general formula (IV), where formula (IV) is:

[0124] [ka]

[0125] (Wherein, radical R 40 , R 41 , R 42 are independent of each other: R 40 = cyano, nitro, acyl or formula -(C=X)-R 43 (In the formula, X=imino or oxygen, R 43 = amino, alkylamino or alkoxy) The radical of R 41 = hydrogen, C1 to C5 alkyl, aryl, benzyl, or acyl; R 42 = Hydrogen or C1 to C5 alkyl (which means)

[0126] Particularly preferably, also in this embodiment, the epoxy resin composition does not contain any further curing agent, co-curing agent, curing accelerator or other catalyst for curing the epoxy resin in addition to the curing agent of general formula (V) or formula (VI) or formula (VII) at all.

[0127] Also preferred is an epoxy resin composition, in particular a liquid epoxy resin composition, comprising an epoxy resin, in particular a liquid epoxy resin, and a curing agent for curing said epoxy resin selected from the group of curing agents according to formula (V) or formula (VI) or formula (VII), and at least one boronic acid of general formula (I), wherein formula (I) is:

[0128] [ka]

[0129] (Wherein, radical R 1 teeth: R 1 = alkyl, hydroxyalkyl or a radical of formula (II) wherein formula (II) means

[0130] [ka]

[0131] (In the formula, R 2 , R 3 , R 4 are independent of each other, R 2 , R 3 , R 4 = Hydrogen, fluorine, chlorine, bromine, iodine, cyano, C1 to C5 alkyl, alkoxy, acyl, alkylsulfonyl, aryl, carboxyl, or B(OH)2 and at least one radical R 2 , R 3 , R 4 represents a group that is not hydrogen, Formula (V) is:

[0132] [ka]

[0133] and the radical R 6 , R 7 , R 9 , R 10 are independent of each other: R 6 , R 7 = independently of each other hydrogen or C1 to C5 alkyl, in particular methyl or ethyl, R 9 , R 10 = independently of each other hydrogen or C1 to C5 alkyl, in particular hydrogen, methyl or ethyl means, Formula (VI) is

[0134] [ka]

[0135] in which the radicals may simultaneously or independently of one another be: R 6 , R 7 = independently of each other hydrogen or C1 to C5 alkyl, in particular methyl or ethyl; R 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 , R 20 = independently of each other hydrogen, C1 to C5 alkyl, in particular methyl or ethyl, or -NHC(O)NR 6 R 7 C1 to C5 alkyl substituted with, in particular -NHC(O)NR 6 R 7 Methyl or ethyl substituted with means, Radical R 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 or R 20 One of them is -NHC(O)NR 6 R 7 and C1 to C5 alkyl substituted with Formula (VII) is

[0136] [ka]

[0137] and the radical R6 , R 7 are independent of each other: R 6 , R 7 = independently of each other hydrogen or C1 to C5 alkyl, in particular methyl or ethyl means, The epoxy resin composition does not contain any curing agent, co-curing agent, curing accelerator or other catalyst for curing the epoxy resin other than the curing agent of general formula (V), or formula (VI) or formula (VII).

[0138] According to a further idea, it is also an object of the present invention to provide an epoxy resin composition, in particular a liquid epoxy resin composition, consisting of at least one epoxy resin, in particular at least one liquid epoxy resin, and a curing agent for curing said epoxy resin and the curing agent consisting of at least one boronic acid of general formula (I), at least one urea derivative according to formula (V) or formula (VI) or formula (VII).

[0139] According to the present invention, the epoxy resin composition comprises at least one epoxy resin, in particular a liquid epoxy resin. Preferably, the epoxy resin or liquid epoxy resin is a polyether having at least one, preferably at least two epoxy groups, even more preferably at least three epoxy resin groups. These epoxy resins or liquid epoxy resins may have at least one, preferably at least two epoxy groups, and may be saturated or unsaturated, aliphatic, cycloaliphatic, aromatic or heterocyclic. Furthermore, these epoxy resins or liquid epoxy resins may have substituents such as halogen, phosphorus and hydroxyl groups. Bisphenol-based epoxy resins, in particular bisphenol A diglycidyl ether as well as bromine-substituted derivatives (tetrabromobisphenol A) or bisphenol F diglycidyl ether, novolac epoxy resins, in particular epoxy phenol novolac or aliphatic epoxy resins, are preferably used in this context. Particularly preferred are epoxy resins based on the glycidyl polyethers of 2,2-bis-(4-hydroxyphenyl)propane (bisphenol A) and bromine-substituted derivatives (tetrabromobisphenol A), 2,2-bis-(4-hydroxyphenyl)methane (bisphenol F) and glycidyl polyethers of novolaks, as well as those based on aniline or substituted anilines such as p-aminophenol or 4,4'diaminodiphenylmethane. Particularly preferred are epoxy resins based on the glycidyl polyethers of 2,2-bis(4-hydroxyphenyl)-propane (bisphenol A) and 2,2-bis(4-hydroxyphenyl)methane (bisphenol F).

[0140] Further preferably, according to the invention, epoxy resins, in particular liquid epoxy resins, can be used which have EEW (epoxide equivalent weight) values ​​in the range of EEW=100 to 1500 g / eq, in particular in the range of EEW=100 to 1000 g / eq, in particular in the range of EEW=100 to 600 g / eq, further preferably in the range of EEW=100 to 400 g / eq, very particularly preferably in the range of EEW=100 to 300 g / eq.

[0141] The cure profile of the formulations of the present invention can be altered by adding additional commercially available additives, such as those known to those skilled in the art for curing epoxy resins.

[0142] Reactive diluents and thermoplastic additives are commonly used in prepreg, towpreg and adhesive formulations, i.e., in addition to the epoxy resin, hardener and boronic acid, the epoxy resin composition according to the present invention may also include a reactive diluent and / or a thermoplastic additive.

[0143] In particular, glycidyl ethers can be used as reactive diluents in the process according to the invention or in the epoxy resin matrix. In this context, monofunctional, di- and polyfunctional glycidyl ethers can be preferably used. In particular, glycidyl ethers, diglycidyl ethers, triglycidyl ethers, polyglycidyl ethers and multiglycidyl ethers as well as combinations thereof should be mentioned. Particularly preferred are 1,4-butanediol diglycidyl ether, trimethylolpropane triglycidyl ether, 1,6-hexanediol diglycidyl ether, cyclohexanedimethanol diglycidyl ether, C8-C 10 Alcohol glycidyl ether, C 12 -C 14Glycidyl ethers selected from the group including alcohol glycidyl ethers, cresol glycidyl ethers, poly(tetramethylene oxide) diglycidyl ether, 2-ethylhexyl glycidyl ether, polyoxypropylene glycol diglycidyl ether, polyoxypropylene glycol triglycidyl ether, neopentyl glycol diglycidyl ether, p-tert-butylphenol glycidyl ether, polyglycerol multiglycidyl ether, and combinations thereof may be used.

[0144] Very particularly preferred glycidyl ethers are 1,4-butanediol diglycidyl ether, trimethylolpropane triglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, cyclohexanedimethanol diglycidyl ether, and combinations thereof.

[0145] Typically, thermoplastic additives are selected from the group of phenoxy resins, acrylates, acrylics, acrylonitriles, polyetherimides, polyarylketones or polysulfone polymers. Due to their positive influence on the flow behavior during processing and on the mechanical properties of the cured components, phenoxy resins, polyacrylates or polysulfones are preferably used.

[0146] Additives for improving the processability of the uncured epoxy resin composition or for adapting the thermomechanical properties of the thermoset product to the requirement profile include, for example, fillers, rheological additives such as thixotropic or dispersing additives, defoamers, dyes, pigments, toughness modifiers, impact modifiers, nanofillers, nanofibers, or fire retardant additives.

[0147] The amount of boronic acid used according to the present invention, as well as the amount of hardener in the epoxy resin composition, can be adjusted according to the present invention with respect to the amount of epoxy resin used.Preferably, based on 100 parts by weight of epoxy resin, in particular 0.05 to 3.0 parts by weight of boronic acid according to formula (I), more preferably 0.1 to 2.0 parts by weight of boronic acid according to formula (I), particularly preferably 0.1 to 1.0 parts by weight of boronic acid according to formula (I) can be used.

[0148] Furthermore, based on 100 parts by weight of epoxy resin, in particular from 1 to 15 parts by weight of a hardener, in particular from the group of hardeners according to formula (III) or formula (V) or formula (VI) or formula (VII), can be used. Further preferably, according to the invention, at least 2 parts by weight of hardener, more preferably at least 3, more preferably at least 4, even more preferably at least 5, very particularly preferably at least 6 parts by weight of hardener can be used in each case based on 100 parts by weight of epoxy resin, independently of which further preferably up to 14 parts by weight of hardener, more preferably up to 13 parts by weight, more preferably up to 12 parts by weight, even more preferably up to 11 parts by weight, very particularly preferably up to 10 parts by weight of hardener can be used in each case based on 100 parts by weight of epoxy resin.

[0149] That is to say, the epoxy resin composition according to the invention preferably comprises, based on 100 parts by weight of epoxy resin, in particular from 4 to 12 parts by weight, very particularly preferably from 6 to 10 parts by weight, of a hardener, in particular from the group of the hardeners according to formula (III) or formula (V) or formula (VI) or formula (VII).

[0150] In this regard, the epoxy resin composition may preferably comprise a hardener and a boronic acid in a weight ratio of hardener to boronic acid corresponding to a ratio in the range of from 1:1 to 300:1, more preferably from 2:1 to 120:1, and particularly preferably from 6:1 to 100:1.

[0151] As mentioned above, the epoxy resin compositions described herein can be stored for relatively long periods of time without any observed hardening. Moreover, these epoxy resin compositions exhibit a hardening profile that allows for a wide range of applications. However, the epoxy resins according to the present invention are particularly suitable for use in fiber composites.

[0152] Thus, the use of epoxy resin compositions of the type described herein for the production of fiber composites, prepregs and towpregs is also within the scope of the present invention.

[0153] Fiber composites such as prepregs or towpregs are characterized by the fact that they are pre-impregnated, partially cured fiber composites consisting of epoxy resin and fibers. These partially cured materials are in the so-called B-stage, partially cured state. In this state, progressive curing of the corresponding epoxy resin composition can continue to occur, since it is only partially cured. In the case of epoxy resin formulations based on epoxy resin-uron mixtures, the corresponding fiber composites such as prepregs and towpregs can continue to react at room temperature, i.e. this can have a negative effect on the desired properties and quality of the fiber composites. That is, longer storage at room temperature is not possible. In order to ensure adequate storage stability of fiber composites such as prepregs or towpregs, they must be stored at controlled low temperatures, often at -18°C. This leads to considerable additional costs and great efforts during storage, transportation and processing of the prepregs and towpregs. It is therefore advantageous if the epoxy resin composition used ensures high latency, which extends the storage conditions of fibre composites such as prepregs and towpregs in a way that is favourable to their properties and quality. The epoxy resin composition according to the invention exhibits high latency to a certain extent, i.e. the epoxy resin composition according to the invention of the type described herein is particularly suitable for solving this problem.

[0154] Likewise, the fibre composite material itself is also the subject of the invention, which is a) a carrier material, in particular reinforcing fibers, and b) Epoxy resin composition according to the present invention Includes.

[0155] Fiber composites, especially prepregs and towpregs, are used for the manufacture of fiber composite parts in very different industrial sectors. For example, fiber composites are used in the automotive industry to manufacture interior trims or fenders or in the aerospace industry for a wide variety of parts. Furthermore, fiber composites are also used to manufacture sports and leisure goods such as tennis rackets or bicycle frames, as well as rotor blades for wind turbines. All types of fibers known to those skilled in the art can be used for these fiber composites. For example, glass, carbon, aramid, plastic, basalt, and natural fibers or rock wool are used. These fiber composites can be processed by autoclaving, deautoclaving, vacuum bagging and pressing methods.

[0156] With regard to the choice of the support material used, in particular reinforcing fibres, more preferably reinforcing fibres selected from the group consisting of carbon fibres, glass fibres, aramid fibres and basalt fibres, can be used according to the invention.

[0157] These reinforcing fibers may further preferably be provided or used in the form of filaments, threads, yarns, woven fabrics, braided fabrics or knitted fabrics.

[0158] In addition, the reinforcing fibers can also be selected from silicon carbide, aluminum oxide, graphite, tungsten carbide, boron. In addition, the reinforcing fibers can also be selected from the group of natural fibers, such as seed fibers (e.g. kapok, cotton), bast fibers (e.g. bamboo, hemp, kenaf, flax) or leaf fibers (e.g. henequen, abac, etc.). Similarly, combinations of these reinforcing fibers can also be used as carrier materials.

[0159] As mentioned above, the epoxy resin compositions described herein can be stored for relatively long periods without hardening being observed. Moreover, these epoxy resin compositions have a hardening profile that shows a wide range of applications. The epoxy resins according to the present invention are therefore also particularly suitable for use in 1K adhesives (one-component adhesives) and acoustic insulation materials. These adhesives and insulation materials are used, for example, in automobile and aircraft construction.

[0160] Thus, the use of an epoxy resin composition of the type described herein for the manufacture of a 1K adhesive or an acoustic insulation material is also a subject of the present invention.

[0161] Numerous adhesives or acoustic insulation materials based on 1K epoxy resin compositions are available for use in a liquid, medium to high viscosity state. On an industrial scale, they must be brought to the appropriate processing temperature before use. Since the barrel is preferably used for a fully continuous mass production, the adhesive or acoustic insulation material contained in the barrel must be processed by a barrel heating mat or, more often, by the melting plate of the barrel melting system. The use of a melting plate attached to the stamp of the barrel melting system places the epoxy resin composition under certain thermal stress. Since the stamp must be pressed against the epoxy resin to transport the molten epoxy resin-based adhesive or acoustic insulation material, the pressure of the stamp against the barrel contents creates additional shear forces that further heat the epoxy resin locally to a high degree. The molten resin must then be transported through a small hose connection attached to the stamp, which usually leads to an application head or assembly gun or melter. This pressure and temperature concentrated stress has a negative effect on the pot life, leading to a decrease in the incubation time of the epoxy resin composition. As a result, the properties of the adhesive or acoustic insulation material may be reduced. It is therefore advantageous if the epoxy resin compositions used for adhesives and acoustic insulation materials ensure high latency in order to ensure a high latency extension during stress as well as during storage of the material, which is favorable for the adhesive and insulating properties and thus for the quality: the epoxy resin compositions according to the invention of the type described herein are particularly suitable for solving this problem. EXAMPLES

[0162] Materials used Product name: EPIKOTE (trademark) Resin 828 (Hexion Inc.) Unmodified bisphenol A epoxy resin (EEW=184~190g / eq) (Viscosity at 25℃ = 12~14Pa * s)

[0163] Urea 1: 1,1'-(4-methyl-m-phenylene)-bis-(3,3-dimethylurea) (AlzChem Trostberg GmbH) Difunctional hardener according to formula V, solid material (particle size 98%≦10μm)

[0164] Urea 2: 1,1'-(methylenedi-p-phenylene)bis[3,3-dimethylurea] (AlzChem Trostberg GmbH) Difunctional hardeners according to formula VII, solid materials

[0165] Urea 3: N'-[3-[[[(dimethylamino)carbonyl]amino]methyl]-3,5,5-trimethylcyclohexyl]-N,N-dimethylurea (AlzChem Torstberg GmbH) Difunctional hardeners according to formula VI, solid materials

[0166] Product Name: 3-Fluorophenylboronic acid; (abcr GmbH) Solid substance, (melting point = 220°C)

[0167] Product Name: 2,5-Dimethoxyphenylboronic acid; (Alfa Aesar) Solid substance (purity = 98%; melting point = 92-94°C)

[0168] Product Name: 1-Octylboronic acid; (Alfa Aesar) Solid substance (purity = 97%; melting point = 81-85°C)

[0169] Product Name: 1,4-Benzenediboronic Acid (Alfa Aesar) Solid material (purity = 96%; melting point > 300°C)

[0170] Product Name:Toray T700 16500d 24k Unidirectional carbon fiber (basis weight 314g / m 2 )

[0171] Preparation of mixtures For the investigation of the formulations described in the examples, the individual components of each formulation are mixed in a mortar for several minutes until homogeneity is achieved. The formulations listed in Table 1 were converted to 10 g of epoxy resin for this purpose.

[0172] Production of fiber composite materials and their test specimens To produce the fiber composites, 6 layers of Toray T700 16500d 24k carbon fiber are cut to 15 cm x 13 cm. In a mortar, the individual components of each formulation are mixed for a few minutes at 40 °C until homogeneity is achieved. The formulations listed in Table 2 were converted to 100 g of epoxy resin for this purpose. The carbon fibers are stacked in one direction and manually laminated with the formulation.

[0173] The impregnated fibers are cured between two aluminum plates at 120° C. for 2 hours. Formulations 4 and K are cured at 120° C. for 2 hours and at 130° C. for 1 hour, respectively. After curing, the fiber composite is removed from the aluminum plate. Corresponding test specimens are subsequently cut from the fiber composite for the determination of the glass transition temperature by dynamic mechanical thermal analysis (DMTA-Tg) according to EN ISO 11357-1 and ASTM D 4065, the mechanical measurement of the interlaminar shear strength (ILSS) according to EN ISO 14130, and the mechanical measurement of the flexural properties by a three-point bending test according to EN ISO 14125.

[0174] JPEG2024505019000030.jpg49158

[0175] Methods used to characterize the composition DSC Survey DSC measurements are carried out on a dynamic differential heat flow calorimeter DSC1 or DSC3 (Mettler Toledo).

[0176] a) Determination of Tg: For the determination of the maximum glass transition temperature (final Tg), a sample of the cured formulation is subjected to the following DSC temperature program: heating from 30 to 200° C. at 20 K / min, holding at 200° C. for 10 min, cooling from 200 to 50° C. at 20 K / min, holding at 50° C. for 5 min, heating from 50 to 200° C. at 20 K / min, holding at 200° C. for 10 min, cooling from 200 to 50° C. at 20 K / min, holding at 50° C. for 5 min, heating from 50 to 220° C. at 20 K / min. The glass transition temperature is determined by applying the tangent to the inflection point of the maximum change in heat capacity (ΔCp) from the last two heating cycles in each case, and the average value is indicated as final Tg.

[0177] b) Isothermal DSC: A sample of the formulation is always held at the specified temperature for the specified time (isothermal cure of the formulation). Evaluation is performed by determining the time to 90% conversion of the exothermic reaction peak (as a measure of the end of the curing process).

[0178] c) Latency time To determine the incubation time (storage stability), about 10 g of each formulation is freshly prepared and then stored in a heating cabinet at a temperature of 40° C. The progressive crosslinking (hardening) of the formulation under these storage conditions is recorded by periodically measuring the dynamic viscosity. The dynamic viscosity is measured using a Haake viscometer [cone (1°) plate method, measurement at 25° C., shear rate 5.0 s -1 The formulation is classified as storage stable (still suitable for processing) until the viscosity has doubled.

[0179] Mechanical Investigation The interlaminar shear strength (ILSS) and flexural properties (3-point bending test) of the fiber composite materials are determined on a Zwick Z010 materials testing machine. The testXpertII software is used to evaluate the measurement results.

[0180] a)ILSS(EN ISO 14130): The test pieces of the fiber composite material are measured at a test speed of 1 mm / min. The radius of the compression fin is 5 mm and the radius of the support is 2 mm. The support width (distance between two supports) is L=10 mm.

[0181] b) Three-point bending test (EN ISO 14125): The test pieces of the fiber composite material are measured at a test speed of 1 mm / min. The radius of the compression fin is 5 mm and the radius of the support is 2 mm. The support width (distance between two supports) is L=80 mm.

[0182] Dynamic mechanical thermal analysis DMTA measurements are performed using an Anton Paar's Modular Compact Rheometer MCR 302 with a Convection Heating System CTD 450 and analysis is performed using Anton Paar's RHEOPLUS / 32 software.

[0183] a) DMTA-Tg (EN ISO 11357-1 and ASTM D 4065): For the determination of the glass transition temperature in fiber composites, the samples are subjected to an oscillatory deformation of 0.01% for 30 minutes at a frequency of 1 Hz. The samples are heated from 50 to 200° C. at 5 K / min. The normal force is −0.5 N. The midpoint Tg of the sample is given as the glass transition temperature.

[0184] Carbon Fiber Content The carbon fiber content of the fiber composite is given as a mass fraction. The mass of the carbon fiber and the mass of the fiber composite made therefrom are determined and a quotient is formed therefrom.

[0185] List of Results

[0186] [Table 1a]

[0187] [Table 1b]

[0188] Explanation and evaluation of the results from Tables 1a and 1b Comparison of Examples A to D according to the invention with Reference Example 1 and Examples E to H according to the invention with Reference Example 2, each consisting of a uron-based hardener in a commercial epoxy resin, shows that comparable characteristic values ​​can be determined for the curing process when using boronic acids according to the invention. This can be determined from values ​​obtained from DSC analysis, including by determining the final Tg and recording an isothermal DSC at 140° C. to determine the 90% conversion of the cure. The incubation time measurements confirm that by adding boronic acids according to the invention, the incubation time at 40° C. can be extended for Examples A to D and E to H. There is an increase in the incubation time of 6 to 12 times for Examples A to D compared to Reference Example 1. There is an increase in the incubation time of 8 to 12 times or more for Examples E to H compared to Reference Example 2. That is, the results from the incubation time measurements of Example F show that a doubling of the viscosity has not yet been achieved in the applied measurement period. For Example F, the result is a 1.6-fold increase in viscosity when measurements were stopped after 96 days. Since Reference Example 2 achieves a 1.6-fold increase in viscosity after 6 days, this results in a 16-fold increase in incubation time for Formulation F.

[0189] That is, the comparison of formulation reference 1 and formulations A to D and formulation reference 2 and formulations E to H shows that the boronic acid according to the invention allows epoxy resin-based prepregs, towpregs and adhesives to achieve extended incubation times of more than 18 weeks at 40° C. while having unchanged curing properties. For the craftsmen, manufacturers and users of prepregs, towpregs and adhesives and acoustic insulation materials, this means easier handling of these products, such that they can be stored, transported and processed without refrigeration. For products according to the correspondingly described formulations A to H based on the boronic acid according to the invention, this results in more than 16 times longer shelf life and storability, especially for prepregs, towpregs and adhesives. This can lead to fewer rejects, less waste and thus reduced costs. This reduces the consumption of expensive raw materials such as carbon fiber and protects the environment.

[0190] [Table 2]

[0191] Description and evaluation of results from Table 2 Comparison of Example 1 according to the invention with Reference Example 3 and Reference Example 4 of K shows that there is no influence on the dynamic mechanical and mechanical properties of the fiber composites by using the epoxy resin composition according to the invention. The determined Tg midpoints of Example 1 according to the invention compared to Reference Example 3 and of K compared to Reference Example 4 are in each case in a constant identical value range. No influence of the epoxy resin composition according to the invention can be detected here. A typical value range can be determined in the mechanical properties of the unidirectional manually laminated fiber composites. The flexural modulus and flexural strength of the respective specimens also confirm the absence of property changes due to the epoxy resin composition according to the invention. The values ​​for the elongation at break are in each case in the same value range. The interlaminar shear strength, which reflects the same load capacity when the layers of the fiber composite are sheared, does not show any significant changes in the fiber composites. Thus, no significant influence of the epoxy resin composition according to the invention can be observed in the mechanical properties either.

[0192] That is, the comparison of formulation references 3 and I and the comparison of formulation references 4 and K show that the boronic acid according to the invention in the fiber composites of epoxy resin-based prepregs and towpregs does not have any change in the final properties of the fiber composite parts. Furthermore, for fiber composites such as prepregs and towpregs, an extended incubation period of more than 18 weeks at 40°C also remains so that the craftsmen, manufacturers and users of prepregs and towpregs obtain consistent fiber composite quality. Furthermore, the production of fiber composites shows that even when using the boronic acid according to the invention, the production process of the fiber composites does not need to be changed or redesigned because the final properties of the parts made therefrom do not change.

Claims

1. 1. Use of a boronic acid of general formula (I) for enhancing the storage stability of an epoxy resin composition comprising an epoxy resin and a curing agent for curing the epoxy resin, wherein formula (I) is: 【Chemistry 1】 (Wherein, the radical R １ teeth: R １ = alkyl, hydroxyalkyl or a radical of formula (II) wherein formula (II) means: 【Chemistry 2】 (In the formula, R ２ , R ３ , R ４ are independent of each other, R ２ , R ３ , R ４ = Hydrogen, fluorine, chlorine, bromine, iodine, cyano, C １ From C ５ Alkyl, alkoxy, acyl, alkylsulfonyl, aryl, carboxyl, or B(OH) ２ and at least one radical R ２ , R ３ , R ４ represents a group that is not hydrogen, The epoxy resin composition comprises as a curing agent a curing agent according to formula (III), where formula (III) is: 【Chemistry 3】 (In the formula, R ６ , R ７ , R ８ are independent of each other, R ６ , R ７ = independently of each other hydrogen or C １ From C ５ Alkyl, R ８ =-NHC(O)NR ６ R ７ C substituted with １ From C １５ Alkyl, -NHC(O)NR ６ R ７ C substituted with ３ From C １５ Cycloalkyl, -NHC(O)NR ６ R ７ or -NHC(O)NR ６ R ７ Alkylaryl substituted with ), The epoxy resin composition does not contain, in addition to the curing agent according to general formula (III), a curing agent selected from the group consisting of cyanamide, guanidine, cyanoguanidine, nitroguanidine, acylguanidine, biguanidine and a curing agent according to general formula (IV), where formula (IV) is as follows: 【Chemistry 4】 (Wherein, the radical R ４０ , R ４１ , R ４２ are independent of each other, R ４０ = cyano, nitro, acyl or the formula -(C=X)-R ４３ (In the formula, X=imino or oxygen; R ４３ = amino, alkylamino or alkoxy) The radical of R ４１ = Hydrogen, C １ From C ５ alkyl, aryl, benzyl, or acyl; R ４２ = Hydrogen or C １ From C ５ Alkyl ), use.

2. The radical R in formula (I) １ but R １ = methyl, ethyl, n-propyl, 1-methylethyl, n-butyl, 1-methylpropyl, 2-methylpropyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decanyl, hydroxymethyl, 2-hydroxyethyl, 3-hydroxypropyl, 4-hydroxybutyl, or 5-hydroxypentyl The use according to claim 1, characterized in that it means:

3. R in formula (I) １ is a radical of formula (II), in which the radical R ２ , R ３ , R ４ but R ２ = Fluorine, Chlorine, Bromine, Iodine, Cyano, C １ - to C ５ -alkyl, alkoxy, acyl, alkylsulfonyl, aryl, carboxyl or B(OH) ２ , R ３ , R ４ = Hydrogen The use according to claim 1, characterized in that it means:

4. R in formula (I) １ is a radical of formula (II), in which the radical R ２ , R ３ , R ４ are independent of each other R ２ , R ３ = independently of each other fluorine, chlorine, bromine, iodine, cyano, C １ From C ５ Alkyl, alkoxy, acyl, alkylsulfonyl, aryl, carboxyl or B(OH) ２ , R ４ = Hydrogen The use according to claim 1, characterized in that it means:

5. R in formula (I) １ is a radical of formula (II), in which the radical R ２ , R ３ , R ４ are independent of each other R ２ , R ３ , R ４ = Fluorine, Chlorine, Bromine, Iodine, Cyano, C １ - to C ５ -alkyl, alkoxy, acyl, alkylsulfonyl, aryl, carboxyl or B(OH) ２ The use according to claim 1, characterized in that it means:

6. An epoxy resin composition comprising at least one epoxy resin and a curing agent for curing the epoxy resin, characterized in that the composition comprises at least one boronic acid of general formula (I), wherein formula (I) is: 【Chemistry 5】 (Wherein, the radical R １ teeth:, R １ = alkyl, hydroxyalkyl or a radical of formula (II) wherein formula (II) means: 【Chemistry 6】 (In the formula, R ２ , R ３ , R ４ are independent of each other, R ２ , R ３ , R ４ = Hydrogen, fluorine, chlorine, bromine, iodine, cyano, C １ From C ５ Alkyl, alkoxy, acyl, alkylsulfonyl, aryl, carboxyl, or B(OH) ２ and at least one radical R ２ , R ３ , R ４ represents a group that is not hydrogen, The epoxy resin composition comprises as a curing agent a curing agent according to formula (III), where formula (III) is: 【Chemistry 7】 (In the formula, R ６ , R ７ , R ８ are independent of each other, R ６ , R ７ = independently of each other hydrogen or C １ From C ５ Alkyl, R ８ =-NHC(O)NR ６ R ７ C substituted with １ From C １５ Alkyl, -NHC(O)NR ６ R ７ C substituted with ３ From C １５ Cycloalkyl, -NHC(O)NR ６ R ７ or -NHC(O)NR ６ R ７ Alkylaryl substituted with ), The epoxy resin composition does not contain, in addition to the curing agent according to general formula (III), a curing agent selected from the group consisting of cyanamide, guanidine, cyanoguanidine, nitroguanidine, acylguanidine, biguanidine and a curing agent according to general formula (IV), where formula (IV) is as follows: 【Chemistry 8】 (Wherein, the radical R ４０ , R ４１ , R ４２ are independent of each other, R ４０ = cyano, nitro, acyl or the formula -(C=X)-R ４３ (In the formula, X=imino or oxygen; R ４３ = amino, alkylamino or alkoxy) The radical of R ４１ = Hydrogen, C １ From C ５ alkyl, aryl, benzyl, or acyl; R ４２ = Hydrogen or C １ From C ５ Alkyl ), an epoxy resin composition.

7. An epoxy resin composition based on 100 parts by weight of epoxy resin a) 1 to 15 parts by weight of a curing agent according to formula (III), and b) 0.05 to 3.0 parts by weight of a boronic acid according to formula (I) The epoxy resin composition according to claim 6, comprising:

8. 8. Epoxy resin composition according to claim 6, characterized in that the weight ratio of hardener to boronic acid corresponds to a ratio in the range of from 1:1 to 300:

1.

9. 9. Use of the epoxy resin composition according to any one of claims 6 to 8 for the production of a fibre composite material.

10. 9. Use of the epoxy resin composition according to claims 6 to 8 for the production of a one-component adhesive or an acoustic insulating material.

11. Use of the epoxy resin composition according to claim 9 for the manufacture of a prepreg or a towpreg.

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