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】 This invention relates to the use of boronic acid to enhance the storage stability of epoxy resin compositions, as well as to epoxy resins, curing agents, and epoxy resin compositions comprising 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 insulation 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 curing agent. 【0003】 The curing of epoxy resins proceeds according to various mechanisms. In addition to curing with phenol or anhydride, curing with amines is often performed. These substances are usually liquids and can be mixed very well with epoxy resins. Due to their high reactivity, such epoxy resin compositions are made using two components. This means that the resin (component A) and the curing agent (component B) are stored separately and mixed in the correct ratio immediately before use. These two-component resin formulations are also called so-called low-temperature curing resin formulations, and thus the curing agent used therein is usually selected from the group of amines or amidoamines. 【0004】 On the other hand, single-component thermosetting epoxy resin formulations are ready for immediate use and pre-assembled; that is, the epoxy resin and curing agent are mixed at the factory. Therefore, mixing errors of individual components during local use are eliminated. A prerequisite for this is a latent curing system that does not react with the epoxy resin at room temperature but readily reacts when heated, depending on the application of energy. In this context, "latent" means that the mixture of individual components is stable under defined storage conditions. 【0005】 For such single-component epoxy resin formulations, dicyandiamide, for example, is particularly suitable and also a cost-effective curing agent. Under ambient conditions, the corresponding epoxy resin-dicyandiamide mixture can be stored ready for use for up to 12 months. 【0006】 To lower the reaction temperature for curing single-component epoxy resin formulations, such as epoxy resin-dicyandiamide mixtures, curing accelerators are commonly added to these formulations to reduce the activation energy for curing, enabling curing at lower temperatures. However, these curing accelerators often reduce the storage stability of the epoxy resin composition containing the epoxy resin, curing agent, and curing accelerator, making long-term storage at room temperature impossible. 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. Similar storage conditions must be maintained when using curing agents with lower latency in epoxy resins. This results in considerable additional costs and effort for the storage, transport, and handling of these formulations, particularly for the manufacture of prepregs, toupregs, or adhesives. 【0007】 Knowing these 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 curing agent for epoxy resins. The composition thus obtained is stable in storage and allows for rapid curing by heating. 【0008】 Furthermore, European Patent Specification EP 2678369 B1 describes a liquid curing agent comprising cyanamide, at least one urea derivative (uron), and at least one organic or inorganic acid as a stabilizer. These curing agents dissolve well in epoxy resins, exhibit high latency in epoxy resins, and enable long-term storage stability. 【0009】 Furthermore, from European Patent Specification EP 2780388 B1, it is known that N,N'-dimethyluron can cure epoxy resins as a single curing agent without the addition of a curing accelerator. 【0010】 Furthermore, European patent application EP 3257884 A1 describes epoxy resin mixtures of epoxy resin, dicyandiamide, aromatic urone, and boric acid esters. The effect of the boric acid esters listed in the examples, particularly the extension of the time to peak in the heat flow curve at 60°C, is so small that it is doubtful whether the addition of these esters can eliminate the need for frozen storage and frozen transport. 【0011】 Furthermore, German patent application DE 10 2019 121 195.6 describes an epoxy resin composition comprising a curing agent, a curing accelerator, and a boronic acid for stabilizing the epoxy resin composition. [Overview of the Initiative] 【0012】 Accordingly, the present invention is directed to provide an epoxy resin composition containing a curing agent that can be stored for a substantial period of several days without any curing being observed. This epoxy resin composition should have high latency below the curing temperature, i.e., high storage stability, and high reactivity at the curing temperature. 【0013】 These problems can be solved by the use described in claim 1 and the epoxy resin composition described in claim 6. Preferred embodiments of the present invention are given in the subclaims, which may be combined with each other as desired. [Modes for carrying out the invention] 【0014】 That is, according to the first embodiment, the use of a boronic acid of general formula (I) for enhancing the storage stability of an epoxy resin composition, particularly a liquid epoxy resin composition, which comprises an epoxy resin, particularly a liquid epoxy resin, and a curing agent for curing the epoxy resin, is the subject of the present invention, where formula (I) is: 【0015】 【Chemical formula】 【0016】 (where the radical R 1 is: R 1 = alkyl, hydroxyalkyl or a radical of formula (II) where formula (II) is: 【0017】 【Chemical formula】 【0018】 (where 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 is not hydrogen), and the epoxy resin composition contains, as a curing agent, a curing agent according to formula (III), where formula (III) is: 【0019】 【Chemical formula】 【0020】 (where R 6 、R7 , R 8 They are independent of each other: R 6 , R 7 = Hydrogen or C1 to C5 alkyl groups, independently of each other. R 8 =-NHC(O)NR 6 R 7 C1 to C replaced by 15 Alkyl, -NHC(O)NR 6 R 7 C3 to C replaced by 15 Cycloalkyl, -NHC(O)NR 6 R 7 aryl or replaced by -NHC(O)NR 6 R 7 alkylaryl substituted with (meaning) The epoxy resin composition does not contain a curing agent selected from the group consisting of cyanamide, guanidine, cyanoguanidine, nitroguanidine, acylguanidine, biguanidine, and a curing agent according to general formula (IV), in addition to a curing agent according to general formula (III) (where formula (IV) is as follows): 【0021】 [ka] 【0022】 (wherein the formula, radical R 40 , R 41 , R 42 They 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) radicals, R 41 = Hydrogen, C1 to C5 alkyl, aryl, benzyl, or acyl, R42 = Hydrogen or C1 to C5 alkyl (This means)). 【0023】 Particularly preferably, the epoxy resin composition contains no further curing agents, co-curing agents, curing accelerators, or other catalysts for curing the epoxy resin, in addition to the curing agent of general formula (III). 【0024】 In other words, according to further embodiments, the use of a boronic acid of general formula (I) to enhance the storage stability of an epoxy resin composition, particularly a liquid epoxy resin, and a curing agent for curing the epoxy resin, is the subject of the present invention, where formula (I) is 【0025】 [ka] 【0026】 (wherein the formula, radical R 1 teeth: R 1 = Alkyl, hydroxyalkyl, or radical of formula (II) This means that, here, equation (II) is, 【0027】 [ka] 【0028】 (In the formula, R 2 , R 3 , R 4 They 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 This means at least one radical R 2 , R 3 , R 4 This represents that (is not hydrogen), The epoxy resin composition comprises a curing agent according to formula (III), where formula (III) is: 【0029】 [ka] 【0030】 (In the formula, R 6 , R 7 , R 8 They are independent of each other, R 6 , R 7 = Hydrogen or C1 to C5 alkyl groups, independently of each other. R 8 =-NHC(O)NR 6 R 7 C1 to C replaced by 15 Alkyl, -NHC(O)NR 6 R 7 C3 to C replaced by 15 Cycloalkyl, -NHC(O)NR 6 R 7 aryl or replaced by -NHC(O)NR 6 R 7 alkylaryl substituted with (meaning) The epoxy resin composition contains no further curing agents, co-curing agents, curing accelerators, or other catalysts for curing the epoxy resin, in addition to the curing agent of general formula (III). 【0031】 Surprisingly, it has been shown that the addition of the boronic acid according to formula (I) of the present invention to an epoxy resin composition containing an epoxy resin and a curing agent according to formula (III) significantly improves the storage stability of the epoxy resin composition, which has thus been prepared for curing. For example, the latent time of a TDI-uron-containing epoxy resin composition can be increased by 6 to 12 times by the addition of the boronic acid according to the present invention (see Examples), and as a result, the corresponding epoxy resin composition can be stored for at least two months longer at room temperature up to 40°C compared to an otherwise identical composition without the addition of the boronic acid according to the present invention, i.e., it can be stored without curing. Quite surprisingly, it has been shown that the desired storage stability is achieved without significantly changing the reactivity of the composition. The addition of the 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 the boronic acid remain unchanged and are essentially maintained. These facts as a whole are surprising. Therefore, as a whole, we can provide an epoxy resin composition that exhibits high storage stability at room temperature and high reactivity at curing temperature, making it extremely suitable for use in prepregs, towpregs, one-component adhesives, and acoustic insulating materials. 【0032】 According to the present invention, an epoxy resin composition means a composition in which the epoxy resin is thermosetting, that is, polymerizable, linkable, and / or crosslinkable by heat due to its functional groups, i.e., epoxy groups. Here, polymerization, linking, and / or crosslinking occur as a result of polyaddition induced by a curing agent. 【0033】 In the context of the present invention, alkyl refers to saturated, linear or branched aliphatic radicals, particularly those of the general formula C n H 2n+1 It should be understood as an alkyl radical having (wherein n represents the number of carbon atoms in the radical). Alkyl can mean a radical having a larger number of carbon atoms. Preferably, alkyl is a radical of the general formula C n H2n+1 This means a saturated, linear or branched aliphatic radical having (wherein n represents the number of carbon atoms in the radical, and n represents a number from 1 to 15). That is, alkyl is preferably C1 to C 15 Alkyl, more preferably C1 to C 10 It means alkyl. Therefore, C1 to C 15 It is even more preferable that the alkyl is 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 means saturated, linear or branched alkyl radicals having up to five carbon atoms. Preferably, C1 to C5 alkyl means 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 present invention, hydroxyalkyl means the alkyl radical as defined above, which is substituted with one, two, or three hydroxyl groups. In particular, according to the present invention, hydroxyalkyl means an alkyl radical having up to 15 carbon atoms and substituted with hydroxyl groups. That is, hydroxyalkyl is preferably C1 to C 15It means hydroxyalkyl. More 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 Cycloalkyls are saturated, monocyclic or bicyclic aliphatic radicals having 3 to 15 carbon atoms, particularly those with the general formula C. n H 2n-1 It is further intended to mean a cycloalkyl radical having (wherein n = an integer from 3 to 15). In this context, C3 to C 15 Cycloalkyl is preferably intended to mean cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, or cycloheptyl, where these cycloalkyl radicals may then be further monosubstituted or polysubstituted with alkyl groups, preferably in the sense described above. 【0037】 According to the present invention, C3 to C 15 Cycloalkyl is particularly preferred, and subsequently, cyclopentyl, cyclohexyl, which may be monosubstituted or polysubstituted with alkyl, particularly 3,3,5,5-tetramethyl-1-cyclohexyl. 【0038】 Cyano represents a nitrile group with the general formula CN. 【0039】 Nitro represents the functional group with the general formula NO2. 【0040】 Amino refers to a functional group with the general formula NH2. 【0041】 The imino represents a functional group with the general formula NH. 【0042】 Alkylamino is a compound of the formula NH. n (Alkyl) 2-nThis refers to a radical (n=0 or 1), where alkyl is an alkyl radical in the sense described above, and the bond site is located on the nitrogen. 【0043】 Carboxyl refers to a functional group with the general formula COOH. 【0044】 Alkoxy means an O-alkyl radical, where alkyl is an alkyl radical in the sense described above, and the bonding site is located on oxygen. According to the present invention, alkoxy means an alkoxy radical in which the alkyl radical has up to 15 carbon atoms, and especially up to 5 carbon atoms. That is, alkoxy is preferably C1 to C 15 Alkoxy more preferably means C1 to C5 alkoxy. Particularly preferably, alkoxy means methoxy, ethoxy, n-propoxy, n-butoxy, or n-pentoxy. 【0045】 The acyl is given by formula C(O)-R 5 This means the fibrous part, and here, R 5 The acyl radical is bonded to carbon and hydrogen, and alkyl or alkoxy can be as described above, with the acyl radical's bonding site located on carbon. Particularly preferably, acyl means formyl or acetyl. 【0046】 Furthermore, alkylsulfonyl means a radical of the formula SO2-alkyl, where both the binding site of the alkylsulfonyl radical and the alkyl radical are located on sulfur, and alkyl is an alkyl radical in the sense described above. According to the present invention, alkylsulfonyl specifically means an alkylsulfonyl radical whose alkyl radical has up to 15 carbon atoms. That is, alkylsulfonyl is preferably C1 to C 15 Alkylsulfonyl more preferably means C1 to C5 alkylsulfonyl. Particularly preferably, alkylsulfonyl means methylsulfonyl, ethylsulfonyl, n-propylsulfonyl, n-butylsulfonyl, or n-pentylsulfonyl. 【0047】 According to the present 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 C6 monosubstituted with aryl, especially benzylphenyl or subsequently arylalkyl, especially arylmethyl, especially phenylmethyl. 15 This means an aryl radical. Particularly preferably, aryl means phenyl, naphthyl, anthryl, phenanthryl, pyrenyl, or perilenyl, most preferably phenyl. 【0048】 Furthermore, according to the present invention, alkylaryl means the above type of aromatic radical, which is then monosubstituted or polysubstituted with the above type of alkyl. In particular, alkylaryl means an aromatic radical having 6 to 15 carbon atoms. That is, alkylaryl is preferably C6 to C 15 This means alkylaryl. More preferably, alkylaryl means methylphenyl, dimethylphenyl, or trimethylphenyl. 【0049】 According to the present invention, the boronic acid of formula (I) can be employed or used, where R in formula (I) 1 R can mean an alkyl, hydroxyalkyl, or radical of formula (II). Preferably, R in formula (I). 1 R can be an alkyl or hydroxyalkyl, where more preferably R 1 It is provided that this has the following meanings. 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 It can also be a radical of formula (II) in which at least one of the substituents R 2 , R 3 , R 4 is not hydrogen. That is, alternatively, R 1 in formula (I) is preferably a radical R 2 , R 3 , R 4 in formula (II) being: R 2 = fluorine, chlorine, bromine, iodine, cyano, C1 - C5 alkyl, alkoxy, acyl, alkylsulfonyl, aryl, carboxyl or B(OH)2, R 3 , R 4 = hydrogen which can mean a radical of formula (II). 【0051】 More preferably, R 1 in formula (I) is a radical R 2 , R 3 , R 4 in formula (II) being: R 2 = fluorine, acyl, alkoxy or B(OH)2, R 3 , R 4 = hydrogen which can mean a radical of formula (II). 【0052】 Even more preferably, R 1 in formula (I) is a radical R 2 , R 3 , R 4 in formula (II) being: R 2 = fluorine, formyl, acetyl, methoxy, ethoxy, n - propoxy, n - butoxy, n - pentoxy, or B(OH)2, R 3 , R 4 = hydrogen which can mean a radical of formula (II). 【0053】 According to further alternatives, a boronic acid according to formula (I) may also be preferably employed or used, where R in formula (I) 1 Preferably, the radical R in formula (II) 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 This means the radical of equation (II). 【0054】 More preferably, R in formula (I) 1 This is the radical R in equation (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 This could be the radical of equation (II), meaning... 【0055】 More preferably, R in formula (I) 1 This is the radical R in equation (II). 2 , R 3 , R 4 but: R 2 , R 3 =Independently of each other, fluorine, formyl, acetyl, methoxy, ethoxy, n-propoxy, n-butoxy, n-pentoxy- or B(OH)2, R 4 = Hydrogen This could be the radical of equation (II), meaning... 【0056】 According to further alternatives, a boronic acid according to formula (I) may be preferably used or employed, where R in formula (I) 1 Preferably, the radical R in formula (II) 2 , R 3 , R 4 They are independent of each other: R 2 , R 3 , R 4 =Fluorine, chlorine, bromine, iodine, cyano, C1-C5 alkyl, alkoxy, acyl, alkylsulfonyl, aryl, carboxyl or B(OH)2 This means the radical of equation (II). 【0057】 More preferably, R in formula (I) 1 This is the radical R in equation (II). 2 , R 3 , R 4 They are independent of each other: R 2 , R 3 , R 4 = Fluorine or C1-C5 alkyl This could be the radical of equation (II), meaning... 【0058】 More preferably, R in formula (I) 1 This is the radical R in equation (II). 2 , R 3 , R 4 They are independent 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 This could be the radical of equation (II), meaning... 【0059】 More 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-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. 【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 a particularly high degree. 【0061】 Very preferably, the compound of formula (III) contains all radicals R 6 and R 7 The curing agent is identical and is particularly methyl, ethyl, n-propyl, i-propyl, n-butyl, or n-pentyl. Preferably, at least two radicals R 6 and two radicals R 7 The radicals are identical, and the radical is selected from the group consisting of methyl, ethyl, n-propyl, i-propyl, n-butyl, and n-pentyl. However, the two radicals R 6 or two radicals R 7 Alternatively, all four groups may also be different from each other, in which case the radical is also preferably selected from the group consisting of methyl, ethyl, n-propyl, i-propyl, n-butyl, or n-pentyl. 【0062】 Therefore, according to further ideas, epoxy resins, in particular liquid epoxy resins, and curing agents for curing said epoxy resins, as well as epoxy resin compositions, in particular liquid epoxy resin compositions, comprising at least one boronic acid of general formula (I), where formula (I) is: 【0063】 [ka] 【0064】 (wherein the formula, radical R 1 teeth: R 1 = Alkyl, hydroxyalkyl, or radical of formula (II) This means that, here, equation (II) is, 【0065】 [ka] 【0066】 (In the formula, R 2 , R 3 , R 4 They 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 This means at least one radical R 2 , R 3 , R 4 This represents that (is not hydrogen), The epoxy resin composition comprises a curing agent according to formula (III), where formula (III) is: 【0067】 [ka] 【0068】 (In the formula, R 6 , R 7 , R 8 They are independent of each other: R 6 , R 7 = Hydrogen or C1 to C5 alkyl groups, independently of each other. R 8 =-NHC(O)NR 6R 7 C1 to C replaced by 15 Alkyl, -NHC(O)NR 6 R 7 C3 to C replaced by 15 Cycloalkyl, -NHC(O)NR 6 R 7 aryl or replaced by -NHC(O)NR 6 R 7 alkylaryl substituted with (meaning) The epoxy resin composition does not contain a curing agent selected from the group consisting of cyanamide, guanidine, cyanoguanidine, nitroguanidine, acylguanidine, biguanidine, and a curing agent according to general formula (IV), in addition to a curing agent according to general formula (III) (where formula (IV) is as follows): 【0069】 [ka] 【0070】 (wherein the formula, radical R 40 , R 41 , R 42 They 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) radicals, R 41 = Hydrogen, C1 to C5 alkyl, aryl, benzyl, or acyl, R 42 = Hydrogen or C1 to C5 alkyl (Meaning) 【0071】 Particularly preferably, also in this embodiment, the epoxy resin composition contains absolutely no additional curing agent, co-curing agent, curing accelerator or other catalyst for curing the epoxy resin, in addition to the curing agent of the general formula (III). 【0072】 That is, an epoxy resin composition, particularly a liquid epoxy resin composition, containing an epoxy resin, particularly a liquid epoxy resin, and a curing agent for curing the epoxy resin is also the subject of the present invention, where the formula (I) is: 【0073】 【Chemical formula】 【0074】 (In the formula, the radical R 1 is: R 1 = alkyl, hydroxyalkyl or a radical of the formula (II) where the formula (II) is: 【0075】 【Chemical formula】 【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 is not hydrogen), which represents), The epoxy resin composition contains a curing agent according to formula (III) as the curing agent, where the formula (III) is: 【0077】 【Chemical formula】 【0078】 (In the formula, R 6 , R 7 , R 8 They 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 by 15 Alkyl, -NHC(O)NR 6 R 7 C3 to C replaced by 15 Cycloalkyl, -NHC(O)NR 6 R 7 aryl or replaced by -NHC(O)NR 6 R 7 alkylaryl substituted with (meaning) The epoxy resin composition contains no further curing agents, co-curing agents, curing accelerators, or other catalysts for curing the epoxy resin, in addition to the curing agent of general formula (III). 【0079】 Further ideas also involve providing an epoxy resin composition, particularly a liquid epoxy resin composition, comprising at least one epoxy resin, in particular at least one liquid epoxy resin, a curing agent for curing the epoxy resin, and at least one boronic acid of general formula (I), wherein the curing agent comprises at least one urea derivative of formula (III). 【0080】 Surprisingly, such epoxy resin compositions were shown to be particularly stable in storage. Specifically, the epoxy resin compositions according to the present invention were shown to have significantly higher storage stability (see examples) compared to known epoxy resin compositions. The epoxy resin compositions according to the present invention can be stored at least 6 to 16 times longer, i.e., by at least a factor of 6 to 16, than equivalent epoxy resin compositions without boronic acid under the same conditions, or have longer storage stability. Very surprisingly, other curing properties of the compositions, such as reactivity, were shown to be comparable to those of known compositions and not significantly changed. That is, these compositions can be excellently used for the manufacture of prepregs, toupregs and one-component adhesives, as well as acoustic insulating materials. 【0081】 The above-described uses, particularly preferred embodiments of the use of boronic acids, also constitute preferred embodiments of the epoxy resin composition of the present invention. That is, the epoxy resin composition of the present invention preferably comprises a boronic acid according to formula (I), where R in formula (I) 1 preferably means alkyl or hydroxyalkyl. More preferably, R in formula (I) 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 This could mean... 【0082】 According to the present invention, R 1 Also, at least one substituent R 2 , R 3 , R 4R may be a radical of formula (II) that is not hydrogen. That is, the epoxy resin composition may or preferably contain a boronic acid according to formula (I), where R 1 This is the radical R in equation (II). 2 , R 3 , R 4 but: R 2 =Fluorine, chlorine, bromine, iodine, cyano, C1-C5 alkyl, alkoxy, acyl, alkylsulfonyl, aryl, carboxyl or B(OH)2, R 3 , R 4 = Hydrogen This is the radical of equation (II), which means... 【0083】 More preferably, R in formula (I) 1 R in equation (II) 2 , R 3 , R 4 but: R 2 = Fluorine, acyl, alkoxy or B(OH)2, R 3 , R 4 = Hydrogen This could be the radical of equation (II), meaning... 【0084】 More preferably, R in formula (I) 1 R in equation (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 This could be the radical of equation (II), meaning... 【0085】 According to further alternatives, the epoxy resin composition may also preferably contain a boronic acid according to formula (I), where R 1 This is the radical R in equation (II). 2 , R3 and R 4 is: R 2 and R 3 = independently of one another, fluorine, chlorine, bromine, iodine, cyano, C1-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 in formula (I) is R 2 and R 3 and R 4 is: R 2 and R 3 = independently of one another, fluorine, acyl, alkoxy or B(OH)2, R 4 = hydrogen and may be a radical of formula (II). 【0087】 Even more preferably, R 1 in formula (I) is R 2 and R 3 and R 4 is: R 2 and R 3 = independently of one another, fluorine, formyl, acetyl, methoxy, ethoxy, n-propoxy, n-butoxy, n-pentoxy or B(OH)2, R 4 = hydrogen and may be a radical of formula (II). 【0088】 According to a further alternative, the epoxy resin composition may alternatively preferably also contain a boronic acid according to formula (I), wherein R 1 is the radical R 2 and R 3 and R 4 are independently of one another: R 2 and R 3 and R 4=Fluorine, chlorine, bromine, iodine, cyano, C1-C5 alkyl, alkoxy, acyl, alkylsulfonyl, aryl, carboxyl or B(OH)2 This is the radical of equation (II), which means... 【0089】 More preferably, R in formula (I) 1 R in equation (II) 2 , R 3 , R 4 They are independent of each other: R 2 , R 3 , R 4 = Fluorine or C1-C5 alkyl This could be the radical of equation (II), meaning... 【0090】 More preferably, R in formula (I) 1 R in equation (II) 2 , R 3 , R 4 They are independent 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 This could be the radical of equation (II), meaning... 【0091】 Most preferably, the epoxy resin composition may contain 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 resin, where formula (III) is: 【0093】 [ka] 【0094】 (In the formula, R 6 , R 7 , R 8 They 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 by 15 Alkyl, -NHC(O)NR 6 R 7 C3 to C replaced by 15 Cycloalkyl, -NHC(O)NR 6 R 7 aryl or replaced by -NHC(O)NR 6 R 7 alkylaryl substituted with It represents (meaning). 【0095】 Due to their properties, these urea derivatives are particularly well-suited for the mild curing of epoxy resins and epoxy resin compositions. 【0096】 Among the urea derivatives described by formula (III), aromatic urea derivatives are preferably employed or used in accordance with the present invention. More preferably, radical R 6 , R 7 , R 8 Independent: R 6 , R 7= Independently of each other, C1 to C5 alkyl groups, especially methyl or ethyl, R 8 =-NHC(O)NR 6 R 7 aryl or replaced by -NHC(O)NR 6 R 7 alkylaryl substituted with It is an aromatic urea derivative of formula (III), meaning [the specified formula]. 【0097】 More preferably, radical R 6 , R 7 , R 8 They are independent of each other: R 6 , R 7 = Independently of each other, C1 to C5 alkyl groups, especially methyl or ethyl, R 8 =-NHC(O)NRR 6 R 7 alkylaryl substituted with It is possible. 【0098】 In other words, according to the present invention, the urea derivative according to formula (V) represents the urea derivative according to formula (III), and the urea derivative according to formula (III) is particularly preferred. According to the present invention, formula (V) is: 【0099】 [ka] 【0100】 Therefore, radical R 6 , R 7 , R 9 , R 10 They are independent of each other: R 6 , R 7 = Independently of each other, hydrogen or C1 to C5 alkyl, especially methyl or ethyl, R 9 , R 10 = Independently of each other, hydrogen or C1 to C5 alkyl, especially hydrogen, methyl or ethyl A urea derivative according to formula (V), which means the above, is particularly preferred. 【0101】 Preferably, radical R related to formula (V). 6 , R 7 , R 9 These are methyl radicals, Mean, R 10 ' is 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, radical R 6 , R 7 , R 8 Independently: R 6 , R 7 = Independently of each other, C1 to C5 alkyl groups, especially methyl or ethyl, R 8 =-NHC(O)NR 6 R 7 Arials replaced by, in particular -NHC(O)NR 6 R 7 benzylphenyl substituted with It is possible. 【0103】 In other words, according to the present invention, the urea derivative according to formula (VII) represents the urea derivative according to formula (III), and the urea derivative according to formula (III) is particularly preferred. According to the present invention, formula (VII) is 【0104】 [ka] 【0105】 Therefore, radical R 6 , R 7 , R 9 , R 10 They are independent of each other: R 6 , R 7 = Independently of each other, hydrogen or C1 to C5 alkyl, especially methyl or ethyl A urea derivative according to formula (VII), which means the above, is particularly preferred. 【0106】 Particularly preferred are radicals R related to formula (VII). 6 , R 7 Each of these terms represents methyl. Of particular preference 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 used. Radical R 6 , R 7 , R 8 Independent: R 6 , R 7 = Independently of each other, hydrogen or C1 to C5 alkyl, especially methyl or ethyl, R 8 =-NHC(O)NR 5 R 6 C1 to C replaced by 15 Alkyl or -NHC(O)NR 5 R 6 C3 to C replaced by 15 Cycloalkyl A more preferable aliphatic urea derivative of formula (III) is one that means the above. 【0108】 Even more preferable is R 6 and R 7 This is defined above, in particular methyl or ethyl, and R 3 -NHC(O)NR 1 R 2 C1 to C replaced by 15 It is a cycloalkyl aliphatic urea derivative according to formula (III). 【0109】 In other words, according to the present invention, the urea derivative according to formula (VI) means the urea derivative according to formula (III), and the urea derivative according to formula (III) is particularly preferred. According to the present invention, formula (VI) is: 【0110】 [ka] 【0111】 And here, the radicals are simultaneously or independently of each other: R 6 , R 7 = Independently of each other, hydrogen or C1 to C5 alkyl, especially 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-C5 alkyl or -NHC(O)NR 6 R 7 C1 to C5 alkyl substituted with Meaning, 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 A urea derivative according to formula (VI), which is a C1 to C5 alkyl group substituted with , is particularly preferred. 【0112】 Even more preferable is R 6 and R 7 R is independently methyl or ethyl, 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 , R 20These independently produce hydrogen, methyl, ethyl, and -NHC(O)NR 6 R 7 or -NHC(O)NR 6 R 7 The curing agent contains an aliphatic urea derivative of formula (VI), which is methyl or ethyl substituted with R. Particularly preferred is 1-(N,N-dimethylurea)-3-(N,N-dimethylurea-methyl)-3,5,5-trimethylcyclohexane (i.e., R 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】 In other words, epoxy resin compositions, particularly liquid epoxy resin compositions, also preferably include an epoxy resin, particularly a liquid epoxy resin, and a curing agent for curing the epoxy resin selected from the group of curing agents according to formula (V), formula (VI), or formula (VII), and at least one boronic acid of general formula (I), where formula (I) is: 【0114】 [ka] 【0115】 (wherein the formula, radical R 1 teeth: R 1 = Alkyl, hydroxyalkyl, or radical of formula (II) This means that, here, equation (II) is, 【0116】 [ka] 【0117】 (In the formula, R 2 , R 3 , R 4 They 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 This means at least one radical R 2 , R 3 , R 4 This represents that (is not hydrogen), Equation (V) is: 【0118】 [ka] 【0119】 Represents radical R 6 , R 7 , R 9 , R 10 They are independent of each other: R 6 , R 7 = Independently of each other, hydrogen or C1 to C5 alkyl, especially methyl or ethyl, R 9 , R 10 = Independently of each other, hydrogen or C1 to C5 alkyl, especially hydrogen, methyl or ethyl Meaning, Equation (VI) is, 【0120】 [ka] 【0121】 (In the formula, radicals are either simultaneously or independently of each other: R 6 , R7 = Independently of each other, hydrogen or C1 to C5 alkyl, especially 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, especially methyl or ethyl, or -NHC(O)NR 6 R 7 C1 to C5 alkyl groups substituted with -NHC(O)NR 6 R 7 Methyl or ethyl substituted with Meaning, 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 (A C1 to C5 alkyl group substituted with, Equation (VII) is, 【0122】 [ka] 【0123】 Therefore, radical R 6 , R 7 They are independent of each other: R 6 , R 7 = Independently of each other, hydrogen or C1 to C5 alkyl, especially methyl or ethyl Meaning, The epoxy resin composition does not contain a curing agent selected from the group consisting of cyanamide, guanidine, cyanoguanidine, nitroguanidine, acylguanidine, biguanidine, and a curing agent according to general formula (IV), in addition to a curing agent of general formula (V), formula (VI), or formula (VII), where formula (IV) is: 【0124】 [ka] 【0125】 (wherein the formula, radical R 40 , R 41 , R 42 They 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) radicals, R 41 = Hydrogen, C1 to C5 alkyl, aryl, benzyl, or acyl, R 42 = Hydrogen or C1 to C5 alkyl (This means...) 【0126】 Particularly preferably, in this embodiment as well, the epoxy resin composition contains no further curing agents, co-curing agents, curing accelerators or other catalysts for curing the epoxy resin, in addition to the curing agent of general formula (V), formula (VI), or formula (VII). 【0127】 In other words, epoxy resin compositions, particularly liquid epoxy resin compositions, also preferably include an epoxy resin, particularly a liquid epoxy resin, and a curing agent for curing the epoxy resin selected from the group of curing agents according to formula (V), formula (VI), or formula (VII), and at least one boronic acid of general formula (I), where formula (I) is: 【0128】 [ka] 【0129】 (wherein the formula, radical R 1 teeth: R 1 = Alkyl, hydroxyalkyl, or radical of formula (II) This means that, here, equation (II) is, 【0130】 [ka] 【0131】 (In the formula, R 2 , R 3 , R 4 They 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 This means at least one radical R 2 , R 3 , R 4 This represents that (is not hydrogen), Equation (V) is: 【0132】 [ka] 【0133】 Therefore, radical R 6 , R 7 , R 9 , R 10 They are independent of each other: R 6 , R 7 = Independently of each other, hydrogen or C1 to C5 alkyl, especially methyl or ethyl, R 9 , R 10 = Independently of each other, hydrogen or C1 to C5 alkyl, especially hydrogen, methyl or ethyl Meaning, Equation (VI) is, 【0134】 [ka] 【0135】 (In the formula, radicals are either simultaneously or independently of each other: R 6 , R 7 = Independently of each other, hydrogen or C1 to C5 alkyl, especially 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, especially methyl or ethyl, or -NHC(O)NR 6 R 7 C1 to C5 alkyl groups substituted with -NHC(O)NR 6 R 7 Methyl or ethyl substituted with Meaning, 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 (A C1 to C5 alkyl group substituted with, Equation (VII) is, 【0136】 [ka] 【0137】 Therefore, radical R6 , R 7 They are independent of each other: R 6 , R 7 = Independently of each other, hydrogen or C1 to C5 alkyl, especially methyl or ethyl Meaning, The epoxy resin composition contains no curing agents, co-curing agents, curing accelerators, or other catalysts for curing the epoxy resin, other than curing agents of general formula (V), or formula (VI) or formula (VII). 【0138】 In addition, it is also the subject of the present invention to provide an epoxy resin composition, particularly a liquid epoxy resin composition, comprising at least one epoxy resin, in particular at least one liquid epoxy resin, and a curing agent for curing the epoxy resin, and a curing agent comprising at least one boronic acid of general formula (I) and at least one urea derivative of formula (V), formula (VI), or formula (VII). 【0139】 According to the present invention, the epoxy resin composition comprises at least one epoxy resin, particularly 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, and 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, alicyclic, 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, particularly bisphenol A diglycidyl ether and bromine-substituted derivatives (tetrabromobisphenol A) or bisphenol F diglycidyl ether, novolac epoxy resins, particularly epoxyphenol novolac, or aliphatic epoxy resins are preferably used in this context. Epoxy resins based on glycidyl polyethers of 2,2-bis-(4-hydroxyphenyl)propane (bisphenol A) and bromine-substituted derivatives (tetrabromobisphenol A), glycidyl polyethers of 2,2-bis-(4-hydroxyphenyl)methane (bisphenol F), and glycidyl polyethers of novolac, as well as those based on aniline or substituted anilines such as p-aminophenol or 4,4'-diaminodiphenylmethane, are particularly preferred. Epoxy resins based on glycidyl polyethers of 2,2-bis(4-hydroxyphenyl)-propane (bisphenol A) and glycidyl polyethers of 2,2-bis(4-hydroxyphenyl)methane (bisphenol F) are particularly preferred. 【0140】 More preferably, according to the present invention, epoxy resins, particularly liquid epoxy resins, can be used that have an EEW (epoxide equivalent) value in the range of EEW = 100 to 1500 g / eq, especially in the range of EEW = 100 to 1000 g / eq, especially in the range of EEW = 100 to 600 g / eq, even more preferably in the range of EEW = 100 to 400 g / eq, and very preferably in the range of EEW = 100 to 300 g / eq. 【0141】 The curing profile of the formulation of the present invention can be altered by adding further 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, toupreg, and adhesive formulations. That is, in addition to epoxy resin, curing agent, and boronic acid, the epoxy resin composition according to the present invention may also contain reactive diluents and / or thermoplastic additives. 【0143】 In particular, glycidyl ethers can be used as reactive diluents in the methods according to the present invention or in epoxy resin matrices. In this context, monofunctional, difunctional, and polyfunctional glycidyl ethers can be preferably used. In particular, glycidyl ethers, diglycidyl ethers, triglycidyl ethers, polyglycidyl ethers and multiglycidyl ethers and combinations thereof should be mentioned. Particularly preferred are 1,4-butanediol diglycidyl ether, trimethylolpropane triglycidyl ether, 1,6-hexanediol diglycidyl ether, cyclohexanedimethanol diglycidyl ether, and C8-C 10 Alcohol glycidyl ether, C 12 -C 14Glycidyl ethers selected from the group including alcohol glycidyl ether, cresol glycidyl ether, 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】 The most 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 consisting of phenoxy resins, acrylates, acrylics, acrylonitriles, polyetherimides, polyarylketones, or polysulfone polymers. Phenoxy resins, polyacrylates, or polysulfones are preferred due to their positive influence on flow behavior during processing and the mechanical properties of the cured components. 【0146】 Additives for improving the processability of uncured epoxy resin compositions or for conforming the thermomechanical properties of thermosetting products to a required profile include, for example, rheological additives such as fillers, thixotropic agents or dispersion additives, defoamers, dyes, pigments, toughness modifiers, impact modifiers, nanofillers, nanofibers, or fire retardant additives. 【0147】 The amount of boronic acid used in accordance with the present invention, and the amount of curing agent in the epoxy resin composition, can be adjusted in accordance with the present invention with respect to the amount of epoxy resin used. Preferably, based on 100 parts by weight of epoxy resin, particularly 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), and especially 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, a curing agent can be used, particularly 1 to 15 parts by weight from the group of curing agents, especially those according to formula (III), formula (V), formula (VI), or formula (VII). More preferably, according to the present invention, at least 2 parts by weight of curing agent, more preferably at least 3, more preferably at least 4, even more preferably at least 5, and very preferably at least 6 parts by weight of curing agent can be used based on 100 parts by weight of epoxy resin in each case, and independently thereof, more preferably up to 14 parts by weight of curing agent, more preferably up to 13, more preferably up to 12, even more preferably up to 11, and very preferably up to 10 parts by weight of curing agent can be used based on 100 parts by weight of epoxy resin in each case. 【0149】 In other words, the epoxy resin composition according to the present invention preferably comprises 100 parts by weight of epoxy resin and particularly 4 to 12 parts by weight, very preferably 6 to 10 parts by weight, of a curing agent from the group of curing agents, particularly according to formula (III), formula (V), formula (VI), or formula (VII). 【0150】 In this regard, the epoxy resin composition may preferably contain a curing agent and boronic acid in a weight ratio of curing agent to boronic acid corresponding to a ratio in the range of 1:1 to 300:1, more preferably 2:1 to 120:1, and particularly preferably 6:1 to 100:1. 【0151】 As described above, the epoxy resin compositions described herein can be stored for relatively long periods without observing curing. Furthermore, these epoxy resin compositions exhibit a curing profile that enables a wide range of applications. However, the epoxy resins according to the present invention are particularly suitable for use in fiber composite materials. 【0152】 In other words, the use of epoxy resin compositions of the type described herein for the manufacture of fiber composite materials, prepregs, and toupregs is also within the scope of the present invention. 【0153】 Fiber composite materials such as prepregs or toupregs are characterized by the fact that they are pre-impregnated and partially cured fiber composite materials consisting of epoxy resin and fibers. These partially cured materials are in the so-called B-stage, a partially cured state. In this state, the corresponding epoxy resin composition is only partially cured, and the further curing of the epoxy resin may continue. In the case of epoxy resin formulations based on epoxy resin-uron mixtures, the corresponding fiber composite materials such as prepregs and toupregs may continue to react at room temperature, which can adversely affect the desired properties and quality of the fiber composite material. In other words, longer-term storage at room temperature is not possible. To ensure proper storage stability of fiber composite materials such as prepregs or toupregs, they must be stored at controlled low temperatures, often -18°C. This incurs considerable additional costs and significant effort during the storage, transport, and processing of prepregs and toupregs. Therefore, it is advantageous if the epoxy resin composition used ensures high latency, which extends the storage conditions of fiber composite materials such as prepregs and towpregs to a degree that is favorable to their properties and quality. The epoxy resin compositions according to the present invention exhibit high latency to a certain extent. That is, the type of epoxy resin composition according to the present invention described herein is particularly suitable for solving this problem. 【0154】 Similarly, the fiber composite material itself is also the subject of the present invention, and it is: a) Carrier materials, especially reinforcing fibers, and b) Epoxy resin composition according to the present invention Includes. 【0155】 Fiber composite materials, particularly prepregs and toupregs, are used in the manufacture of fiber composite parts in a wide variety of industrial sectors. For example, fiber composite materials are used in the automotive industry to manufacture interior trim or fenders, or in the aerospace industry for a wide range of parts. Furthermore, fiber composite materials are also used to manufacture sporting goods 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 composite materials. For example, glass, carbon, aramid, plastics, basalt, and natural fibers, or rock wool, are used. These fiber composite materials can be processed by autoclave, deautoclave, vacuum bag, and press methods. 【0156】 With regard to the selection of the carrier material to be used, in particular reinforcing fibers, more preferably reinforcing fibers selected from the group consisting of carbon fibers, glass fibers, aramid fibers, and basalt fibers, can be used in accordance with the present invention. 【0157】 These reinforcing fibers may more preferably be provided or used in the form of filaments, threads, yarns, woven fabrics, braided fabrics or knitted fabrics. 【0158】 Furthermore, the reinforcing fibers can also be selected from silicon carbide, aluminum oxide, graphite, tungsten carbide, and boron. Additionally, the reinforcing fibers can be selected from a 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., henequene, avac). Similarly, combinations of these reinforcing fibers can also be used as carrier materials. 【0159】 As described above, the epoxy resin compositions described herein can be stored for relatively long periods without curing being observed. Furthermore, these epoxy resin compositions have a curing profile that exhibits 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 insulating materials. These adhesives and insulating materials are used, for example, in automobile and aircraft construction. 【0160】 In other words, the use of epoxy resin compositions of the type described herein for the manufacture of 1K adhesives or acoustic insulating materials is also a subject of the present invention. 【0161】 Numerous adhesives or acoustic insulating materials based on 1K epoxy resin compositions are available for use in medium to high viscosity liquid states. On an industrial scale, these must be brought to an appropriate processing temperature before use. Since barrels are preferably used for fully continuous mass production, the adhesives or acoustic insulating materials contained in the barrels must be processed by a barrel heating mat, or often by a molten plate in a barrel melting system. The use of a molten plate attached to a stamp in a barrel melting system places the epoxy resin composition under specific thermal stress. Because the stamp must be pressed against the epoxy resin to transport the molten epoxy resin-based adhesive or acoustic insulating material, the pressure of the stamp against the barrel contents generates additional shear forces that locally further heat the epoxy resin to a high degree. The molten resin must be transported through a small hose connection attached to the stamp, which is typically connected to an application head or assembly gun or melter. This pressure and temperature-concentrated stress has a negative impact on pot life, leading to a decrease in the latency period of the epoxy resin composition. As a result, the properties of the adhesive or acoustic insulating material may be reduced. Therefore, it is advantageous for epoxy resin compositions used for adhesives and acoustic insulating materials to ensure high latency in order to guarantee a high latency extension not only under stress but also during storage, which is advantageous for adhesive and insulating properties and, i.e., quality. That is, epoxy resin compositions of the type described herein according to the present invention 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 ​​= 184-190 g / eq) (Viscosity at 25℃ = 12~14Pa) * s) 【0163】 Urea 1:1,1'-(4-methyl-m-phenylene)-bis-(3,3-dimethylurea) (AlzChem Trostberg GmbH) Bifunctional curing agent according to formula V, solid material (particle size 98% ≤ 10 μm) 【0164】 Urea 2:1,1'-(methylenedi-p-phenylene)bis[3,3-dimethylurea](AlzChem Trostberg GmbH) Bifunctional curing agent according to formula VII, solid material 【0165】 Urea 3:N'-[3-[[[(dimethylamino)carbonyl]amino]methyl]-3,5,5-trimethylcyclohexyl]-N,N-dimethylurea (AlzChem Torstberg GmbH) Difunctional curing agent according to formula VI, solid material 【0166】 Product name: 3-fluorophenylboronic acid; (abcr GmbH) Solid material (melting point = 220°C) 【0167】 Product name: 2,5-Dimethoxyphenylboronic acid (Alfa Aesar) Solid material (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 / m²) 2 ) 【0171】 Preparation of the mixture To investigate the formulations described in the examples, the individual components of each formulation were mixed in a mortar for several minutes until homogeneity was achieved. The formulations listed in Table 1 were converted to 10 g of epoxy resin for this purpose. 【0172】 Manufacturing of fiber composite materials and their test specimens To manufacture the fiber composite material, six layers of Toray T700 16500d 24k carbon fiber were cut into 15cm x 13cm pieces. In a mortar, the individual components of each formulation were mixed at 40°C for several minutes until homogeneity was achieved. The formulations listed in Table 2 were converted to 100g of epoxy resin for this purpose. The carbon fibers were stacked in one direction and laminated manually with the formulation. 【0173】 The impregnated fibers were cured between two aluminum plates at 120°C for 2 hours. Reference formulations 4 and K were cured at 120°C for 2 hours and 130°C for 1 hour, respectively. After curing, the fiber composite material was removed from the aluminum plates. Subsequently, corresponding test specimens were cut from the fiber composite material for measurement of the glass transition temperature by dynamic mechanical thermal analysis (DMTA-Tg) according to EN ISO 11357-1 and ASTM D 4065, mechanical measurement of interlaminar shear strength (ILSS) according to EN ISO 14130, and mechanical measurement of bending properties by a three-point bending test according to EN ISO 14125. 【0174】 JPEG0007874098000030.jpg49158 【0175】 Methods used to characterize composition DSC Survey DSC measurements are performed on a dynamic thermal differential calorimeter (DSC1) or DSC3 (Mettler Toledo). 【0176】 a) Determination of Tg: To determine 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 20K / min, holding at 200°C for 10 minutes, cooling from 200 to 50°C at 20K / min, holding at 50°C for 5 minutes, heating from 50 to 200°C at 20K / min, holding at 200°C for 10 minutes, cooling from 200 to 50°C at 20K / min, holding at 50°C for 5 minutes, and heating from 50 to 220°C at 20K / min. The glass transition temperature is determined in each case by applying a tangent to the inflection point of the maximum change in heat capacity (ΔCp) from the last two heating cycles, and the average value is shown as the final TG. 【0177】 b) Isothermal DSC: A sample of the formulation is kept at a specified temperature for a specified time (isothermal curing of the formulation). Evaluation is performed by determining the time of 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 period (storage stability), approximately 10 g of each formulation is freshly prepared and then stored in a heated cabinet at 40°C. The gradual crosslinking (hardening) of the formulations under these storage conditions is recorded by periodically measuring the dynamic viscosity. Dynamic viscosity is measured using a Haake viscometer [cone (1°) plate method, at 25°C, with a shear rate of 5.0 s]. -1 The determination is made using [ ]. The formulation is classified as having storage stability (still suitable for processing) until its viscosity doubles. 【0179】 Mechanical investigation The interlaminar shear strength (ILSS) and bending properties (three-point bending test) of fiber composite materials are measured on a Zwick Z010 material testing machine. The measurement results are evaluated using testXpertII software. 【0180】 a) ILSS (EN ISO 14130): A test specimen of fiber composite material is 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): A test specimen of fiber composite material is 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 were performed using Anton Paar's Modular Compact Rheometer MCR 302 with a Convection Heating System CTD 450, and analysis was performed using Anton Paar's RHEOPLUS / 32 software. 【0183】 a) DMTA-Tg (EN ISO 11357-1 and ASTM D 4065): To determine the glass transition temperature in fiber composite materials, the sample is subjected to a vibrational deformation of 0.01% at a frequency of 1 Hz for 30 minutes. The sample is 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 material is given as a mass fraction. The mass of the carbon fibers and the mass of the fiber composite material made from them are determined, and a quotient is formed from these. 【0185】 List of results 【0186】 [Table 1a] 【0187】 [Table 1b] 【0188】 Explanation and evaluation of the results from Table 1a and Table 1b Comparisons of Examples A to D according to the present invention with Reference Example 1 and Examples E to H according to the present invention with Reference Example 2, each consisting of a uron-based curing agent in a commercially available epoxy resin, demonstrate that comparable characteristic values ​​for the curing process can be determined when using the boronic acid according to the present invention. This can be determined from values ​​obtained from DSC analysis, including determining the final Tg and recording isothermal DSC at 140°C to determine the 90% conversion of curing. Latency time measurements confirm that the latency at 40°C can be extended for Examples A to D and E to H by adding the boronic acid of the present invention. For Examples A to D compared with Reference Example 1, there is a 6 to 12-fold increase in latency. For Examples E to H compared with Reference Example 2, there is an 8 to 12-fold or more than 12-fold increase in latency. That is, the results from the latency time measurement of Example F indicate that a doubling of viscosity has not yet been achieved during the applied measurement period. For Example F, the result was a 1.6-fold increase in viscosity when measurements were stopped after 96 days. This results in a 16-fold increase in the latency period for formulation F, as Reference Example 2 achieved a 1.6-fold increase in viscosity after 6 days. 【0189】 In other words, the comparison of Formula Reference Example 1 with Formulas A through D, and the comparison of Formula Reference Example 2 with Formulas E through H, demonstrate that the boronic acid according to the present invention enables epoxy resin-based prepregs, towpregs, and adhesives to achieve extended incubation times exceeding 18 weeks at 40°C while maintaining unchanged curing properties. For experts, manufacturers, and users of prepregs, towpregs, adhesives, and acoustic insulation materials, this means easier handling of these products, allowing them to be stored, transported, and processed without refrigeration. For products based on the boronic acid according to the present invention, according to the correspondingly described Formulas A through H, this results in more than 16 times longer shelf life and storability, particularly for prepregs, towpregs, and adhesives. This can lead to fewer defects, less waste, and thus lower costs. This reduces the consumption of expensive raw materials such as carbon fiber and protects the environment. 【0190】 [Table 2] 【0191】 Explanation and evaluation of the results from Table 2 A comparison of Example 1 of the present invention with Reference Example 3 and K with Reference Example 4 demonstrates that using the epoxy resin composition according to the present invention has no effect whatsoever on the dynamic mechanical and mechanical properties of the fiber composite material. The determined midpoint of Tg for Example 1 of the present invention compared with Reference Example 3 and for K compared with Reference Example 4 are within the same range of values ​​in each case. No influence of the epoxy resin composition according to the present invention can be detected here. Typical ranges of values ​​can be determined in the mechanical properties of fiber composite materials laminated by unidirectional manual work. The flexural modulus and flexural strength of each test specimen also confirm the absence of property changes for the epoxy resin composition according to the present invention. The values ​​for elongation at break are within the same range in each case. The interlaminar shear strength, which reflects the same load capacity as when the layers of the fiber composite material are sheared, shows no significant change whatsoever in the fiber composite material. Therefore, no significant influence of the epoxy resin composition according to the present invention can be observed in the mechanical properties either. 【0192】 In other words, the comparison of formulations Reference Examples 3 and I, and formulations Reference Example 4 and K, demonstrates that the boronic acid according to the present invention in epoxy resin-based prepregs and towpregs of fiber composite materials does not cause any change in the final properties of the fiber composite material components. Furthermore, for fiber composite materials such as prepregs and towpregs, an extended incubation period of more than 18 weeks at 40°C remains, allowing skilled prepreg and towpreg manufacturers and users to obtain consistent fiber composite material quality. Moreover, the manufacturing of fiber composite materials does not require modification or redesign of the fiber composite material manufacturing process, even when using the boronic acid according to the present invention, because the final properties of the components made therefrom do not change.

Claims

[Claim 1] The use of a boronic acid of general formula (I) to enhance 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】 (In the formula, radical R １ teeth: R １ = Alkyl, hydroxyalkyl, or radical of formula (II) This means that equation (II) is: 【Chemistry 2】 (In the formula, R ２ , R ３ , R ４ They 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 This means at least one radical R ２ , R ３ , R ４ This represents that (is not hydrogen), The epoxy resin composition comprises a curing agent according to formula (III), where formula (III) is: 【Transformation 3】 (In the formula, R ６ , R ７ , R ８ They are independent of each other, R ６ , R ７ = Hydrogen or C independently of each other １ From C ５ Alkyl, R ８ =-NHC(O)NR ６ R ７ C replaced by １ From C １５ Alkyl, - NHC(O)NR ６ R ７ C replaced by ３ From C １５ Cycloalkyl, - NHC(O)NR ６ R ７ aryl or replaced by - NHC(O)NR ６ R ７ alkylaryl substituted with (meaning) The epoxy resin composition does not contain a curing agent selected from the group consisting of cyanamide, guanidine, cyanoguanidine, nitroguanidine, acylguanidine, biguanidine, and a curing agent according to general formula (IV), in addition to a curing agent according to general formula (III) (where formula (IV) is as follows): 【Chemistry 4】 (In the formula, radical R ４０ , R ４１ , R ４２ They 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) radicals, R ４１ = Hydrogen, C １ From C ５ Alkyl, aryl, benzyl, or acyl, R ４２ = Hydrogen or C １ From C ５ Alkyl (Meaning), use. [Claim 2] Radical R in equation (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 the following. [Claim 3] R in equation (I) １ R is the radical of equation (II), where R is the radical. ２ , R ３ , R ４ but R ２ = Fluorine, chlorine, bromine, iodine, cyano, C １ - from 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 the following. [Claim 4] R in equation (I) １ R is the radical of equation (II), where R is the radical. ２ , R ３ , R ４ They 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 the following. [Claim 5] R in equation (I) １ R is the radical of equation (II), where R is the radical. ２ , R ３ , R ４ They are independent of each other R ２ , R ３ , R ４ = Fluorine, chlorine, bromine, iodine, cyano, C １ - from C ５ - Alkyl, alkoxy, acyl, alkylsulfonyl, aryl, carboxyl or B(OH) ２ The use according to claim 1, characterized in that it means the following. [Claim 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: 【Transformation 5】 (In the formula, radical R １ teeth:, R １ = Alkyl, hydroxyalkyl, or radical of formula (II) This means that equation (II) is: 【Transformation 6】 (In the formula, R ２ , R ３ , R ４ They 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 means and at least one radical R ２ , R ３ , R ４ is not hydrogen) is represented by) The epoxy resin composition comprises a curing agent according to formula (III), where formula (III) is: 【Transformation 7】 (In the formula, R ６ , R ７ , R ８ They 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 replaced by １ From C １５ Alkyl, - NHC(O)NR ６ R ７ C replaced by ３ From C １５ Cycloalkyl, - NHC(O)NR ６ R ７ aryl or replaced by - NHC(O)NR ６ R ７ alkylaryl substituted with (meaning) The epoxy resin composition does not contain a curing agent selected from the group consisting of cyanamide, guanidine, cyanoguanidine, nitroguanidine, acylguanidine, biguanidine, and a curing agent according to general formula (IV), in addition to a curing agent according to general formula (III) (where formula (IV) is as follows): 【Transformation 8】 (In the formula, radical R ４０ , R ４１ , R ４２ They 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) radicals, 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, meaning (i.e., an epoxy resin composition). [Claim 7] 100 parts by weight of epoxy resin-based epoxy resin composition 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 boronic acid according to formula (I) The epoxy resin composition according to claim 6, characterized by containing the following: [Claim 8] The epoxy resin composition according to any one of claims 6 to 7, characterized in that the weight ratio of the curing agent to the boronic acid corresponds to a ratio in the range of 1:1 to 300:

1. [Claim 9] Use of the epoxy resin composition according to any one of claims 6 to 8 for the manufacture of fiber composite materials. [Claim 10] Use of the epoxy resin composition according to any one of claims 6 to 8 for the manufacture of a one-component adhesive. [Claim 11] Use of the epoxy resin composition according to claim 9 for the manufacture of a prepreg or toupreg. [Claim 12] Use of the epoxy resin composition according to any one of claims 6 to 8 for the manufacture of an acoustic insulating material.

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