Method for producing an epoxy resin composition for pre-impregnation of materials

Abstract

The present invention relates to a method for preparing an epoxy resin composition for pre-impregnation of materials, in which a provided epoxy resin is heated to a temperature in the range of 60°C to 100°C and mixed with a curing agent, a curing accelerator, optionally a thickener, and a boronic acid of general formula (I) as a polymerization inhibitor. JPEG2025526245000017.jpg2333

Description

[Technical Field]

[0001] The present invention relates to a method for preparing an epoxy resin composition for pre-impregnation of materials under temperature exposure. [Background technology]

[0002] Epoxy resins are widely used due to their excellent chemical resistance, excellent thermal and dynamic mechanical properties, and high electrical insulating properties. They are available in liquid or solid form and can be cured with or without the addition of a hardener, and with or without heat input.

[0003] Epoxy resins cure by a variety of mechanisms. In addition to curing with phenols or anhydrides, curing with amines is also often used. These substances are usually liquid and are usually very compatible with epoxy resins. Due to their high reactivity, such epoxy resin compositions are two-part. This means that the resin (part A) and the hardener (part B) are stored separately and are mixed in the correct ratio only immediately before use. These two-part resin formulations are also known as cold-cure resin formulations, and the hardeners used for this purpose are usually selected from the group of amines or amidoamines.

[0004] On the other hand, one-component heat-curing epoxy resin formulations are ready to use, i.e., the epoxy resin and hardener are mixed in the factory. This eliminates the possibility of mismixing the components during on-site application. The prerequisite is a latent hardener system, which does not react with the epoxy resin at room temperature but reacts readily upon heating in response to the energy input. In this context, "latent" means that the mixture of components is stable under the specified storage conditions.

[0005] Dicyandiamide, for example, is a particularly suitable and cost-effective hardener for such one-component epoxy resin formulations. Under ambient conditions, the corresponding epoxy resin-dicyandiamide mixtures can be stored in a usable state for up to 12 months.

[0006] To lower the reaction temperature for curing one-component epoxy resin formulations such as epoxy resin-dicyandiamide mixtures, accelerators are usually added to these formulations to lower the activation energy of curing and enable curing at lower temperatures. However, these accelerators reduce the storage stability of the epoxy resin compositions.

[0007] Proposals to overcome such obstacles have already been published. For example, International Patent Specification WO2021 / 023593 describes the use of boronic acids to enhance the storage stability of epoxy resin compositions containing an epoxy resin, a curing agent, and a curing accelerator. The epoxy resin compositions are storage stable and can be rapidly cured by heating.

[0008] Furthermore, International Patent Application PCT / EP2022 / 051177 shows that the use of boronic acids is also advantageous for improving the storage stability of epoxy resin compositions containing an epoxy resin and an uron. In this context, the storage stability of epoxy resin compositions based on N,N-dimethyluronen as a curing agent is improved by the addition of boronic acids.

[0009] In many cases, the introduction of additional additives into epoxy resins requires heating the resin to enable or facilitate uniform mixing of the additives. The presence of accelerators is problematic here because the application of heat increases the reactivity of the epoxy resin composition. Exposure to temperature is particularly necessary in the production of epoxy resin compositions for prepregs or towpregs due to the relatively high viscosity of the epoxy resin composition. When low-viscosity epoxy resin compositions are used at room temperature, thickeners must usually be mixed in. Mixing the epoxy resin and thickener uniformly usually requires heating the epoxy resin. If the epoxy resin already has a viscosity suitable for prepreg or towpreg production, heating the epoxy resin is necessary to mix additional necessary additives, such as curing agents, reaction accelerators, or polymerization inhibitors, with the resin.

[0010] The viscosity is adjusted by adding resins with different viscosities or powder additives, particularly those with higher viscosities. As the viscosity of an epoxy resin composition increases, its dispersibility decreases. Therefore, the temperature must be increased to reduce the viscosity. In this case, the epoxy resin compositions are exposed to high temperatures for several hours to achieve optimal blending of all components, including epoxy resins with various viscosities, curing agents, curing accelerators, and other additives. They are then applied to reinforcing fibers, such as carbon fiber, glass fiber, or basalt fiber, at high temperatures. Summary of the Invention

[0011] The present invention is therefore based on the problem of providing a method for producing an epoxy resin composition suitable for producing materials (e.g., prepregs or towpregs) pre-impregnated with the resin composition. In this context, curing agents, curing accelerators and other additives should be easily incorporated into the epoxy resin composition while maintaining the property profile of the composition required for the production of prepregs or towpregs.

[0012] a) heating the supplied epoxy resin to a temperature in the range of 60°C to 100°C; and b) mixing a boronic acid of general formula (I) as a polymerization inhibitor with the epoxy resin;

[0013] [ka]

[0014] (In the formula, the group R 1 is the following: R 1 = alkyl, hydroxyalkyl or a group of formula (II), Therein, formula (II) is:

[0015] [ka]

[0016] (In the formula, R 2 , R 3 , R 4 are each independently of one another, and the group R 2 , R 3 , R 4 At least one of the is not hydrogen: R 2 , R 3 , R 4 = hydrogen, fluorine, chlorine, bromine, iodine, cyano, C1-C5-alkyl, alkoxy, acyl, alkylsulfonyl, aryl, carboxyl, or B(OH)2), c) mixing a curing accelerator with the epoxy resin to accelerate the curing of the epoxy resin, wherein the curing accelerator comprises a compound of formula (III);

[0017] [ka]

[0018] (In the formula, R 6 , R 7 , R 8 are, independently of each other: R 6 , R 7= independently of each other hydrogen or C1-C5-alkyl, R 8 = Hydrogen, C1 to C 15 -Alkyl, C3-C 15 -cycloalkyl, aryl, alkylaryl, -NHC(O)NR 6 R 7 C1~C substituted with 15 -Alkyl, -NHC(O)NR 6 R 7 C3~C substituted with 15 -cycloalkyl, -NHC(O)NR 6 R 7 aryl substituted with -NHC(O)NR 6 R 7 alkylaryl substituted with d) optionally mixing a curing agent with the epoxy resin, the curing agent comprising cyanamide and / or a compound of formula (IV);

[0019] [ka]

[0020] (In the formula, the group R 40 , R 41 , R 42 are, independently of each other: R 40 = cyano, nitro, acyl or formula (C=X)-R 43 (Wherein X=imino or oxygen, R 43 = amino, alkylamino or alkoxy) groups, R 41 = hydrogen, C1-C5-alkyl, aryl, or acyl, R 42 = hydrogen or C1-C5-alkyl), e) optionally mixing a thickener with the heated epoxy resin from step a); wherein the temperature exposure of the epoxy resin in step a) is at least 15 minutes and should not exceed 240 minutes; and wherein two or more of steps a) to e) of the method can be carried out simultaneously and / or consecutively. The problem is solved by a method for producing an epoxy resin composition for pre-impregnation of materials, characterized in that:

[0021] Since it has been found that epoxy resin compositions which do not contain a curing agent from the group comprising cyanamide and compounds of formula (IV) are also sufficiently reactive, the present invention also provides a process in which process step d) is absent.A preferred process variant includes process step d).

[0022] According to the present invention, an epoxy resin composition refers to a composition in which the epoxy resin is thermosetting (i.e., polymerizable, linkable, or crosslinkable by heat due to its functional groups (i.e., epoxy groups)), where the polymerization, linkage, or crosslinking occurs as a result of polyaddition induced by a curing agent and a curing accelerator.

[0023] In the context of the present invention, alkyl refers to saturated, linear or branched aliphatic groups, in particular groups of the general formula CH n2n+1 where n represents the number of carbon atoms in the group. Alkyl can also mean groups with more carbon atoms. Preferably, alkyl is a group of the general formula CH n2n+1 (wherein n represents the number of carbon atoms in the group, n being a number from 1 to 15). Thus, alkyl preferably represents a C1-C 15 -alkyl, more preferably C1-C 10 -alkyl. More preferably, C1 to C 15 -Alkyl especially 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, 1-ethylpropyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl or n-dodecyl.

[0024] Furthermore, C1-C5-alkyl denotes a saturated, linear or branched alkyl radical having up to 5 carbon atoms. Preferably, C1-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.

[0025] According to the present invention, hydroxyalkyl means an alkyl radical as defined above, which is substituted with one, two or three hydroxy groups. According to the present invention, hydroxyalkyl means in particular an alkyl radical having up to 15 carbon atoms and substituted with a hydroxy group. Hydroxyalkyl is therefore preferably a C1-C 15 -hydroxyalkyl. More preferably, hydroxyalkenyl preferably means C1-C5-hydroxyalkyl. Particularly preferably, hydroxyalkyl means hydroxymethyl, 2-hydroxyethyl, 3-hydroxypropyl, 4-hydroxybutyl or 5-hydroxypentyl.

[0026] 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 a radical of the general formula C n H n2n-1 where n=an integer from 3 to 15. In this context, preferably, 15 -cycloalkyl is intended to mean in particular cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl or cycloheptyl, which cycloalkyl groups can furthermore preferably be mono- or polysubstituted by alkyl as defined above.

[0027] According to the present invention, C3 to C 15-Cycloalkyl particularly preferably denotes cyclopentyl, cyclohexyl, which may be mono- or polysubstituted by alkyl, and especially 3,3,5,5-tetramethyl-1-cyclohexyl.

[0028] Cyano refers to a nitrile group of the general formula CN. Nitro denotes a functional group of the general formula NO2. Amino refers to a functional group of general formula NH2. Imino refers to a functional group of the general formula NH.

[0029] According to the present invention, alkylamino is a group of formula NH n (Alkyl) 2-n where n=0 or 1, alkyl is an alkyl group as defined above, and the attachment site is at the nitrogen. Carboxyl refers to a functional group of the general formula COOH.

[0030] According to the invention, alkoxy means a group of the formula O-alkyl, where alkyl is an alkyl group as defined above and the attachment site is at the oxygen. According to the invention, alkoxy means in particular an alkoxy group whose alkyl group has up to 15 carbon atoms, in particular up to 5 carbon atoms. Thus, alkoxy is preferably a C1-C 15 -alkoxy, more preferably C1-C5-alkoxy. Particularly preferably, alkoxy denotes methoxy, ethoxy, n-propoxy, n-butoxy or n-pentoxy.

[0031] According to the present invention, acyl is a group of formula C(O)-R 5 (In the formula, R 5 means a group attached to a carbon atom and which may be hydrogen, alkyl or alkoxy as defined above, and the point of attachment of the acyl group is located on the carbon atom. Particularly preferably, acyl means formyl or acetyl.

[0032] Furthermore, alkylsulfonyl denotes a radical of the formula SO2-alkyl, where both the bonding site and the alkyl radical of the alkylsulfonyl radical are located on the sulfur, and alkyl is an alkyl radical as defined above. According to the invention, alkylsulfonyl denotes in particular alkylsulfonyl radicals whose alkyl radical has up to 15 carbon atoms. Alkylsulfonyl is therefore preferably a C1-C 15 More preferably, alkylsulfonyl means methylsulfonyl, ethylsulfonyl, n-propylsulfonyl, n-butylsulfonyl or n-pentylsulfonyl.

[0033] According to the present invention, aryl means an aromatic group, in particular an aromatic group having 6 to 15 carbon atoms, which may be monocyclic, bicyclic or polycyclic. Thus, aryl preferably means a C6-C 15 -aryl, where aryl particularly preferably denotes phenyl, naphthyl, anthryl, phenanthryl, pyrenyl or perylenyl, most preferably phenyl.

[0034] Further, according to the present invention, alkylaryl means an aromatic group of the above type, which is mono- or polysubstituted with alkyl of the above type. In particular, alkylaryl means an aromatic group having 6 to 15 carbon atoms. Aryl is therefore preferably a C6-C 15 -alkylaryl, which more preferably means methylphenyl, dimethylphenyl or trimethylphenyl.

[0035] Surprisingly, it has been shown that the addition of the substituted boronic acid of formula (I) of the present invention to an epoxy resin composition containing an epoxy resin, a curing accelerator, and optionally a curing agent minimizes the loss of properties and quality of the epoxy resin composition when exposed to temperature during the manufacturing process of the epoxy resin composition. Surprisingly, the use of the substituted boronic acid of the present invention has been shown to maintain the curing properties and reactivity of the epoxy resin composition even after heating to temperatures ranging from 60°C to 100°C. This means that the quality of the cured properties in the desired prepreg and towpreg is not reduced. Furthermore, it has been shown that the viscosity of the epoxy resin itself is not significantly affected after temperature treatment. Therefore, if necessary, the desired viscosity can be adjusted by adding only a thickener. Therefore, the desired impregnation properties of the epoxy resin composition are maintained. The addition of the substituted boronic acid does not affect the glass transition temperature to be achieved. Therefore, the overall curing properties of the curing agent and curing accelerator achieved without the addition of the substituted boronic acid are not changed and are substantially maintained. Overall, therefore, an epoxy resin composition can be provided that can be subjected to temperature exposure of 60°C to 100°C for several hours without affecting the curing properties, and is therefore highly suitable for use in prepregs or towpregs.

[0036] According to the present invention, substituted boronic acids of formula (I) can be used, in which R 1 can mean alkyl, hydroxyalkyl or a group of formula (II). Preferably, R in formula (I) 1 can mean alkyl or hydroxyalkyl, and more preferably R 1 can have 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.

[0037] In accordance with the present invention, R 1 also refers to the substituent R 2 , R 3 , R 4 may alternatively and preferably be a group of formula (II) where at least one of R 1 can mean a group of formula (II), in which the group R 2 , R 3 , R 4 is: R 2 = fluorine, chlorine, bromine, iodine, cyano, C1-C5-alkyl, alkoxy, acyl, alkylsulfonyl, aryl, carboxyl or B(OH)2, R 3 , R 4 = Hydrogen.

[0038] More preferably, R in formula (I) 1 may be a group of formula (II), wherein R in formula (II) 2 , R 3 , R 4 is: R 2 = fluorine, cyano, acyl, alkylsulfonyl, or B(OH)2, R 3 , R 4 = Hydrogen.

[0039] Even more preferably, R in formula (I) 1 may be a group of formula (II), wherein R in formula (II) 2 , R 3 , R 4 is: R 2 = fluorine, cyano, formyl, acetyl, methylsulfonyl, ethylsulfonyl, n-propylsulfonyl, n-butylsulfonyl, n-pentylsulfonyl, or B(OH)2, R 3 , R 4 = Hydrogen.

[0040] According to a further alternative, R in formula (I)1 may preferably also mean a group of formula (II), in which R 2 , R 3 , R 4 is: R 2 , R 3 = independently fluorine, chlorine, bromine, iodine, cyano, C1-C5-alkyl, alkoxy, acyl, alkylsulfonyl, aryl, carboxyl or B(OH)2, R 4 = Hydrogen.

[0041] More preferably, R in formula (I) 1 may be a group of formula (II), wherein R in formula (II) 2 , R 3 , R 4 is: R 2 , R 3 = independently fluorine or alkoxy, R 4 = Hydrogen.

[0042] Even more preferably, R in formula (I) 1 may be a group of formula (II), wherein R in formula (II) 2 , R 3 , R 4 is: R 2 , R 3 = independently fluorine, methoxy, ethoxy, n-propoxy, n-butoxy or n-pentoxy, R 4 = Hydrogen.

[0043] According to a further alternative, R in formula (I) 1 may also preferably be a group of formula (II), in which the group R 2 , R 3 , R 4 are, independently 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.

[0044] More preferably, R in formula (I) 1 may be a group of formula (II), and R 2 , R 3 , R 4 are, independently of each other: R 2 , R 3 , R 4 = fluorine or C1-C5 alkyl.

[0045] Even more preferably, R in formula (I) 1 may be a group of formula (II), in which the group R 2 , R 3 , R 4 are, 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.

[0046] Particularly preferably, formula (I) denotes 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.

[0047] Surprisingly, such epoxy resin compositions have been shown to be particularly temperature stable in the range above 60°C, thereby facilitating or enabling intimate mixing of epoxy resins with additives or thickeners in the first place. Accordingly, epoxy resin compositions comprising a polymerization inhibitor of formula (I), a cure accelerator of formula (III), and optionally a curing agent or cyanamide of formula (IV) have been shown to have a low tendency to react at temperatures above 60°C up to 100°C, preferably between 65°C and 90°C, and particularly between 70°C and 85°C, for up to 4 hours.

[0048] The temperature exposure of the epoxy resin to mix the individual additives is in the range of 15 minutes to 4 hours, preferably 30 minutes to 3 hours, and particularly 45 minutes to 2 hours. At higher temperatures, shorter times are preferred to avoid significant polymerization in the epoxy resin composition. Therefore, a temperature exposure of 30 to 90 minutes at a temperature of 70°C to 90°C, particularly 30 to 90 minutes at a temperature between 70°C and 90°C, is particularly preferred.

[0049] Surprisingly, other curing properties, such as reactivity and viscosity, of the epoxy resin compositions obtained according to the present invention after heating to 60°C to 100°C were shown to be comparable to the curing and rheological properties of the unmodified compositions. Furthermore, the rheological properties can be easily adjusted by the described method, for example, by using thickeners. Therefore, the epoxy resin compositions obtained by the described method can be well used for pre-impregnation of materials, especially for the production of prepregs or towpregs.

[0050] According to the present invention, a curing agent selected from the group consisting of cyanamide or guanidine, in particular cyanoguanidine, nitroguanidine, acylguanidine or biguanidine, can be used or employed as a curing agent for curing the epoxy resin in step d) of any method. Preferably, cyanamide or a curing agent of general formula (IV) can be used as the curing agent, wherein formula (IV) is as follows:

[0051] [ka]

[0052] (In the formula, the group R 40 , R 41 , R 42 are, independently of each other: R 40 = cyano, nitro, acyl or formula -(C=X)-R 43 (Wherein X=imino or oxygen, R 43 = amino, alkylamino or alkoxy) groups, R 41 = hydrogen, C1-C5-alkyl, aryl, benzyl, or acyl, R 42 = hydrogen or C1-C5 alkyl).

[0053] In this context, R 41 = hydrogen or C1-C5-alkyl and / or R 42 Further preference is given to curing agents of the formula (IV), in which = hydrogen or C1-C5-alkyl, and C1-C5-alkyl simultaneously or independently of one another denotes a methyl, ethyl, n-propyl, isopropyl, n-butyl or n-pentyl group.

[0054] Particularly preferably, hardeners of formula (IV) can be used, to which the following applies: R 40 = cyano or nitro, especially cyano, R 41 = hydrogen, methyl or ethyl, especially hydrogen, R 42 = hydrogen, methyl or ethyl, especially hydrogen.

[0055] As curing agents of general formula (IV) for curing epoxy resins, preferred are cyanoguanidine, 1,1-dimethyl-3-cyanguanidine, 1-acetyl-3-cyanguanidine, 1-(p-chlorophenyl)-3-cyanguanidine, nitroguanidine, 1-methyl-3-nitroguanidine, 1-ethyl-3-nitroguanidine, 1-butyl-3-nitroguanidine, 1-benzyl-3-nitroguanidine, formylguanidine, acetylguanidine, carbamoylguanidine or methoxycarbonylguanidine, particularly preferably cyanoguanidine. These cyanoguanidine or nitroguanidine derivatives are characterized by particularly high latency.

[0056] As an alternative to or in addition to the compound of formula (IV), cyanamide can also be used as a curing agent for curing epoxy resins.

[0057] According to the present invention, urea derivatives can be used or employed as curing accelerators, in particular urea derivatives of formula (III), wherein formula (III) is as follows:

[0058] [ka]

[0059] (In the formula, R 6 , R 7 , R 8 are, independently of each other: R 6 , R 7 = independently of each other hydrogen or C1-C5-alkyl, R 8 = Hydrogen, C1-C 15 -Alkyl, C3-C 15 -cycloalkyl, aryl, alkylaryl, -NHC(O)NR 6 R 7 C1~C substituted with 15 -Alkyl, -NHC(O)NR 6 R 7 C3~C substituted with15 -cycloalkyl, -NHC(O)NR 6 R 7 aryl substituted with -NHC(O)NR 6 R 7 (alkylaryl substituted with ).

[0060] Among the urea derivatives of formula (III) described, preference is given to using aromatic urea derivatives. Further preference is given here to aromatic urea derivatives of formula (III) in which the group R 6 , R 7 , R 8 are independently: R 6 , R 7 = independently of one another C1-C5-alkyl, in particular methyl or ethyl, R 8 = aryl, arylalkyl, or -NHC(O)NR 6 R 7 aryl substituted with, or -NHC(O)NR 6 R 7 and alkylaryl substituted with .

[0061] More preferably, the group R 6 , R 7 , R 8 The can be, independently of each other: R 6 , R 7 = independently of one another C1-C5-alkyl, in particular methyl or ethyl, R 8 =-NHC(O)NR 6 R 7 aryl substituted with -NHC(O)NR 6 R 7 Alkylaryl substituted with, in particular -NHC(O)NR 6 R 7 and alkylaryl substituted with .

[0062] Thus, according to the invention, urea derivatives having formula (V), of which formula (III) is preferred, are particularly preferred, in which formula (V) is:

[0063] [ka]

[0064] (In the formula, the group R 6 , R 7 , R 9 , R 10 are, independently of each other: R 6 , R 7 = independently of one another hydrogen or C1-C5-alkyl, in particular hydrogen, methyl or ethyl, R 9 , R 10 = independently of one another hydrogen or C1-C5-alkyl, in particular hydrogen, methyl or ethyl).

[0065] Preferably, the group R associated with formula (V) 6 , R 7 , R 9 Both represent methyl groups, and R 10 represents 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).

[0066] Among the urea derivatives of formula (III) described, aliphatic urea derivatives can be used more preferably, where the group R 6 , R 7 , R 8 Further preferred are aliphatic urea derivatives of formula (III) which are independently: R 6 , R 7 = independently of one another hydrogen or C1-C5-alkyl, in particular hydrogen, methyl or ethyl, R 8 = Hydrogen or C1-C 15 -Alkyl, C3-C 15 -cycloalkyl, -NHC(O)NR 5 R 6 C1~C substituted with 15 -Alkyl, -NHC(O)NR5 R 6 C3~C substituted with 15 -cycloalkyl.

[0067] R 6 and R 7 is as defined above, in particular hydrogen, methyl or ethyl, and R 8 is hydrogen or C1-C 15 Further preferred are aliphatic urea derivatives according to formula (III) which represent -alkyl, in particular methyl, ethyl, n-propyl, 1-methylethyl, n-butyl, 1-methylpropyl, 2-methylpropyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl or n-decanyl. Particularly preferred are aliphatic urea derivatives according to formula (III) which represent the group R 6 , R 7 Both represent methyl, and R 8 represents n-butyl. N-(n-butyl-)-N',N'-dimethylurea is particularly preferred.

[0068] Further preferred are aliphatic urea derivatives of formula (III), in which R 6 and R 7 is as defined above, in particular hydrogen, methyl or ethyl, and R 3 -NHC(O)NR 1 R 2 C1~C substituted with 15 -cycloalkyl.

[0069] Thus, according to the invention, urea derivatives of formula (III) have the preferred formula (VI), of which formula (VI) is:

[0070] [ka]

[0071] in which the groups are simultaneously or independently of one another: R 6 , R 7= independently of one another hydrogen or C1-C5-alkyl, in particular hydrogen, 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-C5-alkyl substituted with

[0072] Further preferred are cure accelerators comprising aliphatic urea derivatives of formula (VI), in which R 6 and R 7 are simultaneously or independently of each other hydrogen, methyl or ethyl, and R 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 , R 20 are independently hydrogen, methyl, ethyl, -NHC(O)NR 6 R 7 , or -NHC(O)NR 6 R 7 Particularly preferred is 1-(N,N-dimethylurea)-3-(N,N-dimethylureamethyl)-3,5,5-trimethylcyclohexane, hereinafter also referred to as N'-[3-[[[(dimethylamino)carbonyl]amino]methyl]-3,5,5-trimethylcyclohexyl]-N,N-dimethylurea) (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 =R19 =R 18 =R 20 = hydrogen).

[0073] The method described herein preferably results in an epoxy resin composition whose polymerization behavior changes as little as possible after temperature exposure. The epoxy resin composition obtained by this method is preferably characterized by having an onset temperature and / or peak temperature that is at least 5% and up to 20% higher than that of a corresponding epoxy resin that does not contain a polymerization inhibitor after 1 hour of temperature exposure at 80°C, the onset temperature and the peak temperature being determined by dynamic DSC measurement at temperatures from -30°C to 250°C at a heating rate of 10°C / min.

[0074] Particularly preferably, the epoxy resin composition obtained after one hour of temperature exposure at 80°C is characterized in that the onset temperature deviates by a maximum of 3.5% from the onset temperature of the corresponding epoxy resin composition without temperature exposure, and / or the peak temperature deviates by a maximum of 3% from the peak temperature of the corresponding epoxy resin composition without temperature exposure after one hour of temperature exposure at 80°C, the onset temperature and the peak temperature being determined by dynamic DSC measurement at a temperature of -30°C to 250°C at a heating rate of 10°C / min.

[0075] Conversely, in the methods described herein, the temperature exposure can be selected to reach the aforementioned onset or peak temperatures in the dynamic DSC measurement, wherein the duration of heating and the set temperature must be within the ranges defined for step a) of the method.

[0076] In principle, the process steps a), b), c), d) and e) can be carried out in any order. Preferably, the process steps a), b), c), d) and e), in particular the addition of the polymerization inhibitor, the hardening accelerator, the optional hardener and the optional thickener, are carried out successively or simultaneously.

[0077] Selection of a specific process step order may also be appropriate to achieve a desired onset temperature and peak temperature in the resulting epoxy resin composition. For example, it may be useful to add at least a portion of the polymerization inhibitor to the polymer resin before the accelerator, particularly before the curing agent. This is particularly advantageous when the addition of at least a portion of the polymerization inhibitor occurs after the epoxy resin has been heated. Thus, in a preferred embodiment of the process described herein, at least 50 wt. % of the polymerization inhibitor is added before or together with the accelerator, optionally the curing agent, and the thickener.

[0078] Furthermore, it is advantageous not to add the entire amount of thickener to the epoxy resin before mixing with the other additives, so that the viscosity of the mixture remains low until all of the additives are blended in. Thus, in a preferred embodiment of the method described herein, at least 50 wt. % of the thickener is added after or together with the polymerization inhibitor, cure accelerator, and optionally, the curing agent.

[0079] In a further preferred embodiment, at least two, preferably three, or all of the process steps b) through e) are performed simultaneously, reducing the required temperature exposure and process effort. For example, individual additives can be introduced before heating, with homogeneous mixing with the epoxy resin occurring later during heating (process step a). Alternatively, the additives, i.e., polymerization inhibitors, accelerators, curing agents, and thickeners, can be mixed with the epoxy resin after or during heating.

[0080] According to the present invention, rheology modifiers, particularly thermoplastic polymers, can be introduced into epoxy resin compositions as thickeners. Thickeners adjust the flow behavior of the resin so that the resin is less likely to leak out of the prepreg. Furthermore, thickeners also contribute to the mechanical properties of the cured epoxy resin. Typically, thermoplastic additives are selected from the group consisting of phenoxy resins, acrylates, acrylonitrile, polyetherimides, polyetherketones, or polysulfone polymers. Phenoxy resins, polyacrylates, or polysulfones are preferred because of their favorable influence on the flow behavior during processing and the mechanical properties of the cured components. Furthermore, powdered inorganic thickeners, particularly fumed silica, can also be added. These can be added to the epoxy resin composition alone, in combination with one or more thermoplastic polymers, or in combination with one, two, or more thermoplastic polymers.

[0081] The described method allows the viscosity of the resulting epoxy resin composition to be adjusted to enable impregnation of materials (e.g., fibers) during prepreg or towpreg production. Preferably, the viscosity of the epoxy resin composition is adjusted to a range of 10 to 1,000 Pa*s. The temperature for viscosity determination should be between 50°C and 80°C. To measure the viscosity, an Anton Paar MCR302 rheometer equipped with a D-PP25 measuring system (1° measuring cone) with a measuring gap of 0.052 mm is used. A dynamic run from 50°C to 80°C is performed at a rate of 5°C / min. A desirable epoxy resin composition exists when the aforementioned viscosity range is reached during the dynamic measurement run.

[0082] In the context of the present invention, the term "epoxy resin" is understood to mean an epoxy monomer composition. Epoxy resins that are liquid at temperatures below 100°C, particularly below 90°C, are particularly suitable for producing epoxy resin compositions. Preferably, the epoxy resin is a polyether having at least one, preferably at least two, epoxy groups, and more preferably at least three. 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 contain substituents such as halogen, phosphorus, or hydroxyl groups. Bisphenol-type epoxy resins, particularly bisphenol A diglycidyl ether and bromine-substituted derivatives (tetrabromobisphenol A) or bisphenol F diglycidyl ether, novolac-type epoxy resins, particularly epoxy phenol novolac, or aliphatic epoxy resins are preferably used herein. Particularly preferred are epoxy resins based on the glycidyl polyethers of 2,2-bis-(4-hydroxyphenyl)propane (bisphenol A) and its bromine-substituted derivative (tetrabromobisphenol A), 2,2-bis-(4-hydroxyphenyl)methane (bisphenol F), and novolaks, as well as anilines or substituted anilines such as p-aminophenol or 4,4'-diaminodiphenylmethane. In particular, 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) are preferred.

[0083] Further preferred epoxy resins, in particular liquid epoxy resins, can be used in the present invention, having EEW values (epoxy equivalent weights) 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, even more preferably in the range of EEW=100 to 400 g / eq, and very particularly preferably in the range of EEW=100 to 300 g / eq.

[0084] For use in prepregs or towpregs, low-cost liquid epoxy resins are particularly preferred, having a viscosity range of 2-30 Pa*s at 25°C, preferably 8-20 Pa*s, and requiring a thickener to increase viscosity. A preferred resin, EPIKOTE, has a viscosity of 12-14 Pa*s at 25°C. TM Resin 828 serves as an example. The viscosity of epoxy resin compounds is usually specified by the supplier. Alternatively, the viscosity can be measured with a rheometer using an AntonPaar viscometer MCR302 (measuring system D-PP25 (1° measuring cone), measuring gap 0.052 mm). Here, the isothermal viscosity is measured at 25°C by continuous recording of 1 or 0.5 measuring points per minute.

[0085] Particularly preferred are epoxy resins having an onset temperature between 110°C and 150°C and / or a peak temperature between 120°C and 160°C after 1 hour of temperature exposure at 80°C, wherein the onset temperature and the peak temperature are determined by dynamic DSC measurement at a temperature of -30°C to 250°C and a heating rate of 10°C / min, and during the dynamic DSC measurement the epoxy resin already contains a curing accelerator and optionally a curing agent, but does not contain a polymerization inhibitor and a thickener.

[0086] The cure profile of the formulations according to the invention can be altered by the addition of further commercially available additives, such as those known to those skilled in the art for curing epoxy resins.

[0087] Reactive diluents and thermoplastic additives are commonly used in prepreg, towpreg, and adhesive formulations.

[0088] Thus, as part of the claimed method, further additives such as reactive diluents and / or thermoplastic polymers can be added to the epoxy resin.

[0089] In particular, glycidyl ethers can be used as reactive diluents in the process of the present invention. Monofunctional, difunctional, and polyfunctional glycidyl ethers can also be preferably used. In particular, glycidyl ethers, diglycidyl ethers, triglycidyl ethers, polyglycidyl ethers, and multiglycidyl ethers, as well as combinations thereof, are mentioned here. Particularly preferred glycidyl ethers include 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 14 -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.

[0090] 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.

[0091] Additives for improving the processability of the uncured epoxy resin composition or for adapting the thermomechanical properties of the thermoset product to a required profile include, for example, fillers, rheological additives such as thixotropic or dispersing additives, antifoaming agents, dyes, pigments, toughening modifiers, impact modifiers, nanofillers, nanofibers, or fire retardant additives.

[0092] The amount of substituted boronic acid used in the epoxy resin composition, as well as the curing agent and curing accelerator, can be adjusted according to the present invention based on the amount of epoxy resin used. Preferably, based on 100 parts by weight of the epoxy resin, 0.05 to 3.0 parts by weight of the substituted boronic acid of formula (I) can be used, more preferably 0.1 to 2.0 parts by weight of the substituted boronic acid of formula (I), and particularly preferably 0.1 to 1.0 part by weight of the substituted boronic acid of formula (I) can be used.

[0093] Furthermore, in the described process, it is possible to use in particular 1.0 to 15 parts by weight of a curing agent (especially from the group of cyanamides or the group of curing agents of formula (IV)), more preferably 3.0 to 12.0 parts by weight of a curing agent (especially from the group of cyanamides or the group of curing agents of formula (IV)), particularly preferably 4.0 to 10.0 parts by weight of a curing agent (especially from the group of cyanamides or the group of curing agents of formula (IV)), based on 100 parts by weight of epoxy resin.

[0094] According to the described method, preferably, 0.1 to 9 parts by weight of a curing accelerator (especially from the group of curing accelerators of formula (III)), more preferably 0.5 to 5.0 parts by weight of a curing accelerator (especially from the group of curing accelerators of formula (III)), particularly preferably 0.5 to 3.0 parts by weight of a curing accelerator (especially from the group of curing accelerators of formula (III)), can be used, based on 100 parts by weight of the epoxy resin.

[0095] Preferably, the curing agent and the substituted boronic acid are used in the preparation of the epoxy resin composition in a weight ratio of curing agent to substituted boronic acid ranging from 1:1 to 240:1, more preferably from 3:1 to 100:1, and particularly preferably from 6:1 to 40:1.

[0096] Further preferred in the methods described herein are curing accelerators and substituted boronic acids in a weight ratio of curing accelerator to substituted boronic acid in the range of 0.05:1 to 160:1, more preferably 0.5:1 to 50:1, and particularly preferably 0.7:1 to 15:1.

[0097] The epoxy resin compositions produced by the described method are particularly suitable for the production of pre-impregnated materials, in particular prepregs and towpregs made from fiber composites, for the production of fiber composite parts such as those used in the sports and leisure market, the automotive market, the aerospace industry and in the production of rotor blades for wind turbines, in which all types of fibers known to those skilled in the art can be used. Examples of these are inorganic materials, such as chemical fibers from the group of carbon fibers, boron fibers, basalt fibers, glass fibers, quartz fibers, slag fibers, metal fibers, nanotube fibers, ceramic fibers, crystalline fibers, or synthetic polymer materials, such as polyesters, polyamides, polyimides, aramids, polyamidimides, polyacrylics, modacryls, polytetrafluoroethylene, polyethylene, polyetheretherketones, polypropylenes, polychlorides, elastanes, polybenzimidazoles, polyureas, melamines, polyphenylene sulfides, polyvinyl alcohols, Vinalon, polycarbonates, polystyrenes, both fibers with a homopolymer structure and fibers with a copolymer structure, such as random copolymers, gradient copolymers, block copolymers, alternating copolymers, graft copolymers, etc. Chemical fibres or natural polymeric substances, for example from the group of cellulose, cellulose esters, polyactids, alginates, chitin, elastodiens, bio-based polyamides, protein fibres, or plant fibres, for example seed fibres from kapok, cotton, poplar fluff, woolgrass, cattail, silk plants, among others, for example bast fibres such as bamboo, nettle, hemp, jute, mallow, broom, hop, willow bast, flax, ramie, kenaf, sunhemp, castor, punga, among others, leaf fibres from agave, bromeliad, hemp, flax, sugar palm, dwarf palm, yucca, cattail, alfa grass, natural fibres such as fruit fibres from coconut, among others, and also animal fibres, for example silk, spider silk, Anapheseide, Eriseide, Mugaseide,Natural fibers include, but are not limited to, fibers from spinning glands containing Tussah silk, fibers from secretions containing Byssus silk, fibers from hair follicles containing hair and wool from sheep, alpaca, llama, vicuña, guanaco, camel, Angora rabbit, cashmere goat, mohair goat, yak, goat, cattle, and horse, as well as mineral fibers such as glass fiber, quartz fiber, mineral wool, silica fiber, ceramic fiber, and the altered products of the named fibers, such as silk nitrate, copper rayon, and combinations of all the named fibers. Preferred fibers are selected from the group consisting of glass fiber, carbon fiber, aramid fiber, basalt fiber, rock wool fiber, polyethylene fiber, flax fiber, hemp fiber, bamboo fiber, and combinations thereof.

[0098] These fiber composites can be processed by processes such as autoclave, "out-of-autoclave," vacuum bag, and compression molding. [Example]

[0099] Working Example: Materials used Product Name: EPIKOTE TM Resin 828 (Hexion Inc.) Unmodified bisphenol A epoxy resin (EEW=184-190g / eq) (Viscosity at 25°C = 12-14 Pa*s)

[0100] Product Name: DER TM 337(Blue Cube Germany Assets GmbH & Co. KG) Modified semi-solid bisphenol A epoxy resin (EEW=230-250g / eq) (Viscosity at 25°C = 400-800 mPa*s, 70 wt% in diethylene glycol monobutyl ether)

[0101] Product Name: DER TM671(Blue Cube Germany Assets GmbH & Co. KG) Solid epoxy resin (EEW=475~550g / eq) (Melting point = 75-85°C)

[0102] Resin 1: EP EPIKOTE TM Resin 828 + DER TM 671(80wt%+20wt%) DER TM EP EPIKOTE 671 TM The resin was dissolved in Resin 828 at 110°C for 2 hours.

[0103] Product name: DYHARD (registered trademark) 100S (Alzchem Trostberg GmbH) Latent hardener, dicyandiamide, solid (particle size 98%≦10μm)

[0104] Urea 1: 1,1'-(4-methyl-m-phenylene)-bis-(3,3-dimethylurea) (Alzchem Trostberg GmbH) Bifunctional latent accelerator of formula V Solid (particle size 98%≦10μm)

[0105] Product Name: 3-Fluorophenylboronic acid; (abcr GmbH) Solid (melting point = 220°C)

[0106] Product Name: Octylboronic acid; (Alfa Aesar) Solid (purity = 97%, melting point = 81-85°C)

[0107] Product Name: 1,4-Benzenediboronic Acid (Alfa Aesar) Solid (purity 96%, melting point >300℃)

[0108] Preparation of the mixture: To test the formulations described in the examples, the components of each formulation were mixed in a dissolver for several minutes until homogeneous. Each formulation was then divided into three portions. One portion was prepared for prepreg production without temperature exposure and subsequent measurements. One formulation was prepared for prepreg production after mixing with temperature exposure at 60°C for three hours, followed by measurements. One formulation was prepared for prepreg production after mixing at 80°C for one hour, followed by measurements.

[0109] Methods for characterizing compositions DSC Test: DSC measurements are carried out using a dynamic heat flow differential calorimeter DSC 1 or DSC 3 (Mettler Toledo).

[0110] a) Dynamic DSC: The formulation samples are subjected to dynamic DSC measurements at a heating rate of 10° C. / min from −30° C. to 250° C. Evaluations include the enthalpy of the curing reaction, the onset temperature, and the maximum peak.

[0111] b) Isothermal DSC: A sample of the formulation is held constant at a given temperature for a given time (isothermal cure of the formulation). Evaluation is performed by determining the time of 90% turnover (90%-Umsatzes) of the exothermic reaction peak (a measure of the end of the curing process). Additionally, the onset temperature and peak temperature are evaluated. Result list:

[0112] [Table 1]

[0113] Table 1: Description and evaluation of results: Examples A-F and Reference Example 1 describe epoxy resin compositions consisting of a curing agent and a curing accelerator in a commercially available epoxy resin, with or without a substituted boronic acid. Examples A-F and Reference Example 1 were subjected to temperature exposures typical of prepreg and towpreg manufacturing. They were then analyzed by dynamic and isothermal DSC.

[0114] After 3 hours of temperature exposure at 60°C, the epoxy resin composition is characterized by dynamic DSC. Ref. 1 shows that after temperature exposure, the onset temperature decreases by 3% (4°C) and the peak temperature shifts to a lower temperature by 2% (3°C). Isothermal DSC analysis at 140°C for 1 hour shows that after the previous temperature exposure, the time to 90% turnover for Ref. 1 decreases by 12% (2 minutes). After 2 hours of isothermal exposure at 120°C, the time decreases by 20% (8 minutes). Thus, the DSC measurements show that the resulting epoxy resin composition Ref. 1 reacts during temperature exposure, leading to a decrease in the onset and peak temperatures as well as a decrease in the turnover time (Umsatzzeit).

[0115] By using the substituted boronic acids of Examples A to F, there is no decrease in onset or peak temperature in dynamic DSC analysis after temperature exposure. There is no decrease in turnover time in isothermal DSC analysis at 140°C for 1 hour. After 2 hours of temperature exposure at 120°C, a slight decrease in turnover time is observed in Examples A and E, which may be due to the lower amount of boronic acid. These examples are still significantly lower than the turnover time of Comparative Example Ref. 1. Therefore, the higher the proportion of substituted boronic acid according to the present invention, the less the effect of prior temperature exposure on the epoxy resin formulation.

[0116] A 1-hour temperature exposure at 80°C reduces the onset temperature by 6% (9°C) and shifts the peak temperature lower by 4% (6°C) for comparative example Ref.1. Isothermal DSC analysis at 140°C for 1 hour shows that the turnover time for Ref.1 decreases by 18% (3 minutes) due to the prior temperature exposure. A 2-hour temperature exposure at 120°C reduces this value by 24% (10 minutes).

[0117] By using substituted boronic acids according to Examples A-F, there is no decrease in onset or peak temperature in dynamic DSC analysis after temperature exposure. There is no significant decrease in turnover time in isothermal DSC analysis at 140°C for 1 hour. A smaller decrease in turnover time is observed in isolated cases at 120°C for 2 hours, but this remains lower than in Ref. 1. Using a higher amount of substituted boronic acid reduces the effect of prior temperature exposure on the epoxy resin formulation.

[0118] In summary, the use of the substituted boronic acids of Examples A-F according to the present invention significantly inhibits polymerization or reaction during temperature exposure in epoxy resin formulations. Long-term treatment at elevated temperatures does not result in changes to the epoxy resin formulation. The rheological properties of the resulting composition are unchanged. As a result, the quality of prepregs or towpregs produced using the epoxy resin compositions is not affected.

[0119] [Table 2]

[0120] Explanation and evaluation of the results in Table 2: Examples G and H and Comparative Example Ref. 2 describe epoxy resin compositions consisting of a curing agent and a curing accelerator in a commercially available epoxy resin, with and without a substituted boronic acid, respectively. Examples G and H and Ref. 2 were subjected to temperature exposures typical of prepreg and towpreg manufacturing. The resulting epoxy resin compositions were then analyzed by dynamic DSC and isothermal DSC. The examples show that after temperature exposure, Examples G and H according to the present invention have no effect on the properties of the epoxy resin formulation compared to Comparative Example Ref. 2.

[0121] After 1 hour of temperature exposure at 80°C, Comparative Example Ref. 2 shows a 9% (12°C) decrease in onset temperature and a 6% (8°C) shift in peak temperature to a lower temperature in the dynamic DSC test. Examples G to H according to the present invention do not show a significant decrease in onset or peak temperature after temperature exposure.

[0122] Isothermal DSC analysis at 140°C for 1 hour measures a 33% (4 min) decrease in turnover time for Comparative Example Ref. 2 after prior temperature exposure, and a 26% (6 min) decrease at 120°C for 2 hours. The use of substituted boronic acids in Examples G and H also results in decreases in turnover time observed in isothermal DSC analysis. However, these decreases are significantly smaller than those observed in Ref. 2. As expected, increasing the proportion of accelerator in the epoxy resin composition increases its reactivity. Nevertheless, Examples G and H demonstrate that the addition of substituted boronic acids significantly reduces the effect of temperature on the epoxy resin composition.

[0123] In summary, even with increased accelerator ratios, the use of substituted boronic acids in Examples G and H effectively inhibits polymerization and reaction, respectively, during the temperature exposure required to formulate the epoxy resin formulation.

[0124] [Table 3]

[0125] Explanation and evaluation of the results in Table 3: Examples J, K, L, and M, as well as Comparative Examples Ref. 3 and Ref. 4, describe epoxy resin compositions consisting of a curing agent and a cure accelerator in a modified epoxy resin, with and without a substituted boronic acid, respectively. These examples were subjected to temperature exposures typical of prepreg and towpreg manufacturing. The epoxy resin compositions were then analyzed by dynamic and isothermal DSC.

[0126] The obtained epoxy resin compositions are characterized by dynamic DSC after 3 hours of temperature exposure at 60°C. Comparative Examples Ref.3 and Ref.4 show a decrease in onset temperature of 3% (4°C) and 1% (2°C), respectively, and a peak temperature shift to lower temperatures of 2% (3°C) and 1% (1°C), respectively, after temperature exposure. The epoxy resin formulations of Examples J and K or L and M according to the present invention do not show a decrease in onset temperature or peak temperature after measurement.

[0127] At 120°C for 2 hours isothermal, the turnover time is reduced by 20% (8 min) for Ref.3 and 9% (3 min) for Ref.4. By using substituted boronic acids, no significant change in turnover time is observed in isothermal DSC measurements of Examples J, K (compared to Ref.3) and M (compared to Ref.4). Example L shows a slightly smaller reduction in turnover time than Ref.4.

[0128] After 1 hour of temperature exposure at 80°C, dynamic DSC measurements show that Ref. 3 and Ref. 4 experience a 6% (9°C) and 9% (13°C) decrease in onset temperature, respectively, and a 4% (6°C) and 5% (7°C) shift in peak temperature toward lower temperatures. No significant decrease in onset or peak temperature was detected in the examples according to the present invention. After 2 hours of isothermal exposure at 120°C, the turnover time decreases by 22% (8 minutes) for Ref. 3 and 18% (7 minutes) for Ref. 4. By using substituted boronic acids, no significant change in turnover time in isothermal DSC measurements can be detected for Examples J and K, and I and M, respectively. Furthermore, in the case of modified resins, the substituted boronic acids of Examples J, K, L, and M provide sufficient inhibition of polymerization or reaction during temperature exposure in the production of the corresponding epoxy resin formulations. The quality of such resin formulations is maintained, and therefore the quality of pre-impregnated materials such as prepregs and towpregs is also maintained.

Claims

1. a) Heat the supplied epoxy resin to a temperature in the range of 60°C to 100°C, and b) A boronic acid of general formula (I) is mixed with the epoxy resin as a polymerization inhibitor. 【Chemistry 1】 (wherein the group R １ The following are the items: R １ = alkyl, hydroxyalkyl or group of formula (II), Therefore, equation (II) is as follows: 【Chemistry 2】 (In the formula, R ２ , R ３ , R ４ These have independent meanings and are based on R ２ , R ３ , R ４ At least one of them is not hydrogen: R ２ 、 R ３ 、 R ４ = hydrogen, fluorine, chlorine, bromine, iodine, cyano, C １ ~ C ５ - alkyl, alkoxy, acyl, alkylsulfonyl, aryl, carboxyl or B(OH ２ )) c) To accelerate the curing of the epoxy resin, a curing accelerator is mixed with the epoxy resin, wherein the curing accelerator contains a compound of formula (III), 【Transformation 3】 (In the formula, R ６ , R ７ , R ８ These are, independently of each other, the following: R ６ , R ７ = Hydrogen or C independently of each other １ ~C ５ - Alkyl, R ８ = Hydrogen, C １ ~C １５ - Alkyl, C ３ ~C １５ -Cycloalkyl, aryl, alkylaryl, -NHC(O)NR ６ R ７ C replaced by １ ~C １５ -Alkyl, -NHC(O)NR ６ R ７ C replaced by ３ ~C １５ -Cycloalkyl, -NHC(O)NR ６ R ７ aryl or -NHC(O)NR substituted with ６ R ７ (Alkylaryl substituted with) d) optionally mix a curing agent with the epoxy resin, wherein the curing agent comprises cyanamide and / or a compound of formula (IV), 【Chemistry 4】 (wherein the group R ４０ , R ４１ , R ４２ These are, independently of each other, the following: R ４０ =Cyano, nitro, acyl or formula -(C=X)-R ４３ (In the formula, X = imino or oxygen) R ４３ = Amino, alkylamino or alkoxy, R ４１ = Hydrogen, C １ ~C ５ - Alkyl, aryl or acyl, R ４２ = Hydrogen or C １ ~C ５ -Alkyl), e) Optionally, a thickening agent is mixed with the heated epoxy resin from step a), Therefore, the temperature exposure to the epoxy resin in step a) shall be at least 15 minutes and shall not exceed 240 minutes, and two or more steps a) to e) of the method may be carried out simultaneously and / or continuously. A method for producing an epoxy resin composition for pre-impregnation of materials, characterized by the above.

2. The method according to 1, characterized in that, in step a), the epoxy resin is heated to a temperature in the range of 70°C to 90°C.

3. The method according to claim 1 or 2, wherein an epoxy resin containing a curing accelerator and optionally a curing agent, but not a polymerization inhibitor and a thickener, has an onset temperature between 110 and 150°C and / or a peak temperature between 120 and 160°C after 1 hour of exposure to a temperature of 80°C, the onset temperature and the peak temperature being determined by dynamic DSC measurement at a heating rate of 10°C / min at a temperature of -30°C to 250°C.

4. The method according to claim 1 or 2, characterized in that the epoxy resin composition has an onset temperature and / or peak temperature that is at least 5% to as much as 20% higher than that of a corresponding epoxy resin without a polymerization inhibitor after 1 hour of exposure to a temperature of 80°C, wherein the onset temperature and the peak temperature are determined by dynamic DSC measurement at a heating rate of 10°C / min at a temperature of -30°C to 250°C.

5. The method according to claim 1 or 2, characterized in that, after 1 hour of exposure to 80°C, the epoxy resin composition exhibits an onset temperature that deviates by up to 3.5% from the onset temperature of the corresponding epoxy resin composition without temperature exposure, and / or after 1 hour of exposure to 80°C, the peak temperature deviates by up to 3% from the peak temperature of the corresponding epoxy resin composition without temperature exposure, wherein the onset temperature and the peak temperature are determined by dynamic DSC measurement at a heating rate of 10°C / min in the range of -30°C to 250°C.

6. The method according to claim 1 or 2, characterized in that the thickener is selected from the group of thermoplastic polymers such as phenoxy resins, acrylate polymers, acrylonitrile polymers, polyetherimide polymers, polyetherketone polymers, and / or powdered inorganic thickeners, according to step e) of the method.

7. Base R in equation (I) １ The method according to 1 or 2, characterized in that the group is selected from the group consisting of a methyl group, an ethyl group, an n-propyl group, a 1-methylethyl group, an n-butyl group, a 1-methylpropyl group, a 2-methylpropyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decanyl group, a hydroxymethyl group, a 2-hydroxyethyl group, a 3-hydroxypropyl group, a 4-hydroxybutyl group, or a 5-hydroxypentyl group.

8. R in equation (I) １ However, it is the basis of equation (II), and there the base R ２ , R ３ and R ４ At least one of them is fluorine, chlorine, bromine, iodine, cyano, C １ ~C ５ - Alkyl, alkoxy, acyl, alkylsulfonyl, aryl, carboxyl and B(OH) ２ The method according to claim 1 or 2, characterized in that the group is selected from the group consisting of the following.

9. The manufactured epoxy resin composition is based on 100 parts by weight of epoxy resin, a) 0.05 to 3.0 parts by weight of boronic acid of formula (I), b) 0.1 to 9 parts by weight of the curing accelerator of formula (III), and c) 1 to 15 parts by weight of the curing agent of formula (IV) The method according to 1 or 2, characterized by including

10. The method according to 1 or 2, characterized by using a weight ratio of curing agent to boronic acid in the range of 1:1 to 240:1, and / or a weight ratio of curing accelerator to boronic acid in the range of 0.05:1 to 160:1.

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