Potting Compound and Insulating Material

Abstract

Various embodiments include a potting compound comprising: a sterically hindered epoxy resin; and a hardener including a basic compound having a pKB, measured in anhydrous acetonitrile, of 23 or higher.

Claims

1. A potting compound comprising: a sterically hindered epoxy resin; and a hardener including a basic compound having a pKB, measured in anhydrous acetonitrile, of 23 or higher.

2. The potting compound as claimed in claim 1, wherein the hardener comprises a component including the structural element I ##STR00014## wherein R1, R2, R3 and/or R4 each include at least one component selected from the group consisting of: hydrogen, branched or unbranched alkyl, acyl, and/or aryl moieties; and/or form a cycle between R2/R3 and/or R1/R4.

3. The potting compound as claimed in claim 1, wherein the hardener does not include any NH functionality in the molecular structure.

4. The potting compound as claimed in claim 1, wherein the component having the structural element I comprises a ligand in a complex.

5. The potting compound as claimed in claim 1, wherein the hardener comprises a compound DBN, 1,5-diazabicyclo[4.3.0]non-5-ene, CAS No. 3001-72-7, having the structural formula II ##STR00015##

6. The potting compound as claimed in claim 1, wherein the component having the structural element I comprises an adduct with an acrylate, an acrylate derivative, and/or a compound containing oxirane groups.

7. The potting compound as claimed in claim 1, wherein the component having the structural element I comprises: a derivative of the group of the following parent compounds: ##STR00016## 1,4,5,6-tetrahydro-2R-pyrimidine; and/or ##STR00017## 1H-2R-2-imidazoline; where R=methyl, ethyl, propyl, isopropyl, butyl, isobutyl, benzyl, phenyl, fluorine, chlorine, bromine, iodine, hydroxyl, aldehyde, and/or carboxylate.

8. The potting compound as claimed in claim 1, wherein the component having the structural element I comprises a compound selected from the group consisting of: ectoine (CAS No. 96702-03-3) and/or any ectoine derivative, 1,4,5,6-tetrahydropyrimidine (CAS No. 1606-49-1), 1,4,5,6-tetrahydro-2-methylpyrimidine, 1,4,5,6-tetrahydro-2-ethylpyrimidine, 1,4,5,6-tetrahydro-2-propylpyrimidine, 1,4,5,6-tetrahydro-2-isopropylpyrimidine, 1,4,5,6-tetrahydro-2-butylpyrimidine, 1,4,5,6-tetrahydro-2-isobutylpyrimidine, 1,4,5,6-tetrahydro-2-phenylpyrimidine, 1,4,5,6-tetrahydro-2-benzylpyrimidine, 1,4,5,6-tetrahydro-2-fluoropyrimidine, 1,4,5,6-tetrahydro-2-chloropyrimidine, 1,4,5,6-tetrahydro-2-bromopyrimidine, 1,4,5,6-tetrahydro-2-iodopyrimidine, 1,4,5,6-tetrahydro-2-cyanopyrimidine, 2-methyl-2-imidazoline (CAS No. 534-26-9), 2-phenyl-2-imidazoline (CAS No. 936-49-2), 2-benzyl-2-imidazoline (CAS No. 59-98-3), 2,4-dimethyl-2-imidazoline (CAS No. 930-61-0), and 4,4-dimethyl-2-imidazoline (CAS No. 2305-59-1).

9. The potting compound as claimed in claim 1, wherein the hardener comprises a component having n=1 to 4 covalently bonded hydroxyl groups.

10. The potting compound as claimed in claim 1, wherein the hardener comprises a compound having one of the structural formulae V to X: ##STR00018## wherein R1, R2, R3, and R4 each comprise a component selected from the group consisting of H, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, benzyl, and phenyl; and n=1 to 12.

11. The potting compound as claimed in claim 1, wherein the component having the structural element I comprises an adduct with an acrylate and/or an acrylate derivative.

12. The potting compound as claimed in claim 1, wherein the component having the structural element I comprises an adduct with a compound containing oxirane groups and having a defined molecular length.

13. The potting compound as claimed in claim 12, wherein the component having the structural element I comprises an adduct with a glycidyl compound selected from the group consisting of: monoglycidyl ether and/or ester compound, diglycidyl ether and/or ester compound, triglycidyl ether and/or ester compound, and tetraglycidyl ether and/or ester compound.

14. The potting compound as claimed in claim 1, wherein the component having the structural element I comprises an adduct with a compound containing oxirane groups and of defined molecular length having n=1 to n=4 oxirane functionalities.

15. The potting compound as claimed in claim 1, wherein the compound containing oxirane groups comprises a derivative of a higher alcohol selected from the group consisting of: monoethylene glycol (C.sub.2H.sub.4)(OH).sub.2, butanediols (C.sub.4H.sub.8)(OH).sub.2, butenediols (C.sub.4H.sub.6)(OH).sub.2, butynediol (C.sub.4H.sub.4)(OH).sub.2, polyethylene glycols H(OC.sub.2H.sub.4)x(OH).sub.2 with x=1 to 5000, propylene glycol (C.sub.3H.sub.6)(OH).sub.2, polypropylene glycols H(OC.sub.3H.sub.6)x(OH).sub.2 with x=1 to 5000, diethylene glycol (C.sub.2H.sub.8O)(OH).sub.2, propanediols (C.sub.3H.sub.6)(OH).sub.2, neopentyl glycol (C.sub.5H.sub.10)(OH).sub.2, cyclopentanediols (C.sub.5H.sub.8)(OH).sub.2, cyclopentenediols (C.sub.5H.sub.6)(OH).sub.2, glycerol (C.sub.3H.sub.5)(OH).sub.3, pentanediols (C.sub.5H.sub.10)(OH).sub.2, pentaerythritol (C.sub.5H.sub.8)(OH).sub.4, hexanediols (C.sub.6H.sub.12)(OH).sub.2, hexylene glycols (C.sub.6H.sub.12)(OH).sub.2, heptanediols (C.sub.7H.sub.14)(OH).sub.2, octanediols (C.sub.8H.sub.16)(OH).sub.2, polycaprolactonediols, polycaprolactonetriols, hydroquinone (C.sub.6H.sub.4)(OH).sub.2, resorcinol (C.sub.6H.sub.4)(OH).sub.2, (pyro)catechol (C.sub.6H.sub.4)(OH).sub.2, rucinol (C.sub.10H.sub.12)(OH).sub.2, triethylene glycol (C.sub.6H.sub.12)(OH).sub.2, fully aromatic, partly hydrogenated and/or fully hydrogenated bisphenol A (C.sub.15H.sub.14)(OH).sub.2, (C.sub.15H.sub.28)(OH).sub.2, bisphenol F (C.sub.13H.sub.10)(OH).sub.2, bisphenol S (C.sub.12H.sub.8O.sub.2S)(OH).sub.2, and tricyclodecanedimethanol (C.sub.12H.sub.18)(OH).sub.2, glycerol carbonate (C.sub.4H.sub.5)(OH).sub.1.

16. The potting compound as claimed in claim 1, wherein the hardener has a nitrogen density D in the range from 1 mmol/g to 15 mmol/g.

17. The potting compound as claimed in claim 1, wherein the hardener comprises compounds of the following structure types XI to XIV: ##STR00019## wherein R1, R2 and R3 each comprise a substance selected from the group consisting of: methyl, ethyl, propyl, isopropyl, butyl, isobutyl, benzyl, and phenyl; and x=1 to 12 and n=1 to 4.

18. The potting compound as claimed in claim 1, wherein the hardener comprises up to 25% by weight of the potting compound, based on the total mass of the potting compound.

19. The potting compound as claimed in claim 1, further comprising additives, flame retardants, and/or reactive diluents.

20-24. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0088] FIG. 1 shows, according to Gelnorm®, temperature-dependent gelation times for various compounds incorporating teachings of the present disclosure.

[0089] FIG. 2 shows the glass transitions in DBN (5% by weight) in ECC molding material after 10 h at 145° C.

[0090] FIG. 3 shows differential calorimetry analysis of anionically initiated homopolymerization of ECC with DBN as catalyst.

[0091] FIG. 4 shows the Tg characteristic of the ECC cured with 5% DBN.

DETAILED DESCRIPTION

[0092] The teachings of the present disclosure describe a potting compound comprising a sterically hindered epoxy resin, e.g. an aliphatic and/or cycloaliphatic epoxy resin, and a hardener comprising a basic compound that exhibits the structural element I

##STR00007##

[0093] where R1, R2, R3 and/or R4 are the same or different and are, for example, hydrogen, branched or unbranched alkyl, acyl and/or aryl moieties and/or form at least one cycle especially via bridge formation between R2/R3 and/or R1/R4, where, in an advantageous embodiment, R4=H. Some embodiments include an insulation material obtainable by casting and curing this potting compound, and an insulation system comprising such an insulation material for electrical insulation. Finally, the teachings describe the use of the potting compound, in filler-containing or filler-free form, by anionic gelation and/or curing as casting resin, infusion resin, impregnation resin and/or encapsulating resin in electrical engineering.

[0094] Insulation materials incorporating teachings of the present disclosure are used, for example, for insulation and/or encapsulation in electrical engineering. In particular, they serve as winding insulation in electrical machines such as transformers, cast resin dry-type transformers etc. as main insulation. The potting compounds are used here, for example, via vacuum pressure impregnation after curing for encapsulation of insulating winding tapes. Contrary to the prior art—the anionic homopolymerization—i.e. the polymerization of identical monomer units—especially of cycloaliphatic, sterically hindered, glycidyl ester- and glycidyl ether-free epoxy resin is possible without use of hardeners based on acid anhydrides.

[0095] The class of epoxy resins described here, as well as the sterically hindered cycloaliphatic epoxy resin ECC (3,4-epoxycyclohexylmethyl 3′,4′-epoxycyclohexanecarboxylate), also generally includes aliphatic hindered epoxy resins, for example epoxidized soybean oils. Exclusively the glycidyl ether- and glycidyl ester-free sterically hindered epoxy resins, in aliphatic or cycloaliphatic form, are discussed here as a basis for potting compounds in the present disclosure. According to widespread scientific opinion (cf. thesis by A. M. Tomuta, New and improved thermosets based on epoxy resins and dendritic polyesters (2014), Universitat Rovira i Virgili, Departament de Química Analítica i Química Orgànica, Tarragona, Spain; see page 5 and page 9) and the generally accepted prior art, it is not possible to anionically homopolymerize cycloaliphatic or aliphatic epoxy resins. This thesis from 2014 explicitly says that “cycloaliphatic epoxy resins cannot be cured by anionic initiators”. Anionic initiators, as the person skilled in the art knows, bring about a basic and not an acidic curing reaction.

[0096] The acidic, especially Lewis-acidic, ring opening by means of superacidic protons known to date, as set out above, owing to the higher ring stress in the cycloaliphatic epoxy resin, for instance ECC, leads to quantitative opening and hence to virtually complete homopolymerization. Anionic activation with standard nucleophilic tertiary, secondary and primary amine hardeners, for example with 1-alkylimidazoles, dimethylbenzylamine, Jeffamines, diethylenetriamine, triethylenetetramine, isophoronediamine, aminoethylpiperazine, diaminocyclohexane, diaminodiphenylmethane, phenylenediamine or diaminophenyl sulfone, leads to only extremely slow gelation, if any, even at high temperatures of 70-90° C., or to only soft hardening, if any, to give the shaped body.

[0097] However, it has been found, surprisingly, and in an unforeseeable manner to the person skilled in the art, that certain nonacidic superbases are indeed capable of gelating a sterically hindered epoxy resin at temperatures of 70-100° C. that are customary in the art, especially an aliphatic epoxy resin, for example a cycloaliphatic epoxy resin such as the advantageous diepoxide ECC, with moderate accelerator contents, and of homopolymerizing it in the course of curing at 145° C. over 10 h to give the faultless shaped body. In some embodiments, strong superbases having pKB values complementary to those of the superacid used to date are suitable for functioning as hardener for the sterically hindered epoxy resins.

[0098] In some embodiments, the formulation includes superbases which, for the conjugated acid, measured in anhydrous acetonitrile, show a MeCNpKBH+ value of 23.5 or higher. In some embodiments, the hardener is a superbase having at least one structural element I

##STR00008##

[0099] where R1, R2, R3 and/or R4 are the same or different and are, for example, hydrogen, branched or unbranched alkyl, acyl and aryl moieties and form a cycle via bridge formation between R2/R3 and/or R1/R4, where, in some embodiments, R4=H.

[0100] In some embodiments, the hardener does not have any NH functionalities in the molecular structure. To improve the ease of handling and processibility of the hardener, especially also to improve the stability under air and/or the vacuum stability of the hardener, it can be used in the form of an adduct and/or a complex, especially complexed to a metal salt. The term “complex” or “complexed” is used here in the organometallic sense of the word, i.e. in such a way that the hardener is attached to a central atom as ligand, but by no means provides all ligands of the complex around the central atom. It is accordingly also possible for other ligands that do not assume any hardener function in the sterically hindered epoxy resin to be provided in the complex used.

[0101] In some embodiments, the basic hardener with the structural element I shown above is used in the form of a copper and/or zinc salt, for instance as Zn(SCN).sub.2*(DBN).sub.2 or Zn(Cl).sub.2*(DBN).sub.2.

[0102] In some embodiments, the hardener comprises 1,5-diazabicyclo[4.3.0]non-5-ene, CAS No. 3001-72-7, referred to hereinafter as “DBN” for short, having the structural formula II

##STR00009##

[0103] In some embodiments, the basic hardener having the structural element I shown above is used in the form of a copper and/or zinc salt, for instance as Zn(SCN).sub.2*(DBN).sub.2 or Zn(Cl).sub.2*(DBN).sub.2. Since DBN is a very mobile compound at room temperature that has only relatively low vacuum stability at higher temperatures, in addition to sole use as hardener, it may be useful to couple the molecule or the active environment responsible for the homopolymerization of ECC covalently to other molecules of higher molecular weight, such as compounds containing acrylate, acrylate derivative and/or oxirane groups, in order thus to increase vacuum stability.

[0104] The following structures show illustrative parent compounds for hardener components:

##STR00010##

[0105] 1,4,5,6-tetrahydro-2R-pyrimidines parent compound or base structure which is present in pure form and/or as derivative in the hardener, and/or

##STR00011##

[0106] 1H-2R-2-imidazoline as parent compound or base structure which is present in pure form and/or as derivative in the hardener; where R=methyl, ethyl, propyl, isopropyl, butyl, isobutyl, benzyl, phenyl, fluorine, chlorine, bromine, iodine, hydroxyl, aldehyde, carboxylate.

[0107] The abovementioned structures III and IV can be reacted efficiently with acrylates such as TMPTA (trimethylolpropane triacrylate), trimethylolpropane propoxylate triacrylate, pentaerythritol tetraacrylate (PETA), dipentaerythritol penta-acrylate/dipentaerythritol hexaacrylate and/or compounds containing oxirane groups and of defined molecular length for stabilization.

[0108] For example, an adduct of one of the following compounds with an acrylate or an acrylate derivative and/or a compound containing oxirane groups and having a defined molecular length is used as hardener:

[0109] ectoine (CAS No. 96702-03-3) and/or any ectoine derivative,

[0110] 1,4,5,6-tetrahydropyrimidine (CAS No. 1606-49-1),

[0111] 1,4,5,6-tetrahydro-2-methylpyrimidine,

[0112] 1,4,5,6-tetrahydro-2-ethylpyrimidine,

[0113] 1,4,5,6-tetrahydro-2-propylpyrimidine,

[0114] 1,4,5,6-tetrahydro-2-isopropylpyrimidine,

[0115] 1,4,5,6-tetrahydro-2-butylpyrimidine,

[0116] 1,4,5,6-tetrahydro-2-isobutylpyrimidine,

[0117] 1,4,5,6-tetrahydro-2-phenylpyrimidine,

[0118] 1,4,5,6-tetrahydro-2-benzylpyrimidine,

[0119] 1,4,5,6-tetrahydro-2-fluoropyrimidine,

[0120] 1,4,5,6-tetrahydro-2-chloropyrimidine,

[0121] 1,4,5,6-tetrahydro-2-bromopyrimidine,

[0122] 1,4,5,6-tetrahydro-2-iodopyrimidine,

[0123] 1,4,5,6-tetrahydro-2-cyanopyrimidine,

[0124] 2-methyl-2-imidazoline (CAS No. 534-26-9),

[0125] 2-phenyl-2-imidazoline (CAS No. 936-49-2),

[0126] 2-benzyl-2-imidazoline (CAS No. 59-98-3),

[0127] 2,4-dimethyl-2-imidazoline (CAS No. 930-61-0),

[0128] 4,4-dimethyl-2-imidazoline (CAS No. 2305-59-1), and any mixtures of the aforementioned compounds.

[0129] In addition, in some embodiments, the hardener comprises, for example, a component with n=1 to 4 covalently bonded hydroxyl groups per molecule. For example, addition products present in the hardener on their own or in the form of any desired mixtures in advantageous working examples of the present invention may be the following compounds having the structural formulae V to X:

##STR00012##

[0130] where

[0131] R1, R2, R3 and R4=H, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, benzyl, phenyl

[0132] and n=1 to 12.

[0133] In some embodiments, in the hardener, the binding of the superbase to the structural unit I, for stabilization thereof, may also be to a compound containing oxirane groups and of defined molecular length, for example to a glycidyl compound, for example a glycidyl ether or glycidyl ester compound, especially one having fewer than 50 carbon atoms. For example, the binding is to a compound containing oxirane groups and of defined molecular length that has n=1 to 4 oxirane functionalities per molecule.

[0134] For example, it is possible here to use the following oxirane-containing compounds, especially glycidyl compounds, the adducts of which with the component containing the structural unit I are present in the hardener:

[0135] monoglycidyl ether and/or ester compound (n=1),

[0136] diglycidyl ether and/or ester compound (n=2),

[0137] triglycidyl ether and/or ester compound (n=3) and/or

[0138] tetraglycidyl ether and/or ester compound (n=4), and any mixtures of the compounds mentioned.

[0139] In some embodiments, the glycidyl compound may be derived from a bisphenol, diol, triol and/or higher alcohol, for example from the group of the following compounds:

[0140] monoethylene glycol (C.sub.2H.sub.4)(OH).sub.2,

[0141] butanediols (C.sub.4H.sub.8)(OH).sub.2,

[0142] butenediols (C.sub.4H.sub.6)(OH).sub.2,

[0143] butynediol (C.sub.4H.sub.4)(OH).sub.2,

[0144] polyethylene glycols H(OC.sub.2H.sub.4)x(OH).sub.2 with x=1 to 5000,

[0145] propylene glycol (C.sub.3H.sub.6)(OH).sub.2,

[0146] polypropylene glycols H(OC.sub.3H.sub.6)x(OH).sub.2 with x=1 to 5000,

[0147] diethylene glycol (C.sub.2H.sub.8O)(OH).sub.2,

[0148] propanediols (C.sub.3H.sub.6)(OH).sub.2,

[0149] neopentyl glycol (C.sub.5H.sub.10)(OH).sub.2,

[0150] cyclopentanediols (C.sub.5H.sub.8)(OH).sub.2,

[0151] cyclopentenediols (C.sub.5H.sub.6)(OH).sub.2,

[0152] glycerol (C.sub.3H.sub.5)(OH).sub.3,

[0153] pentanediols (C.sub.5H.sub.10)(OH).sub.2,

[0154] pentaerythritol (C.sub.5H.sub.8)(OH).sub.4,

[0155] hexanediols (C.sub.6H.sub.12)(OH).sub.2,

[0156] hexylene glycols (C.sub.6H.sub.12)(OH).sub.2,

[0157] heptanediols (C.sub.7H.sub.14)(OH).sub.2,

[0158] octanediols (C.sub.8H.sub.16)(OH).sub.2,

[0159] polycaprolactonediols, polycaprolactonetriols, hydroquinone (C.sub.6H.sub.4)(OH).sub.2,

[0160] resorcinol (C.sub.6H.sub.4)(OH).sub.2,

[0161] (pyro)catechol (C.sub.6H.sub.4)(OH).sub.2,

[0162] rucinol (C.sub.10H.sub.12)(OH).sub.2,

[0163] triethylene glycol (C.sub.6H.sub.12)(OH).sub.2 [0164] fully aromatic, partly hydrogenated and/or fully hydrogenated bisphenol A (C.sub.15H.sub.14)(OH).sub.2, (C.sub.15H.sub.28)(OH).sub.2, bisphenol F (C.sub.13H.sub.10)(OH).sub.2, bisphenol S (C.sub.12H.sub.8O.sub.2S)(OH).sub.2 [0165] tricyclodecanedimethanol (C.sub.12H.sub.18)(OH).sub.2, glycerol carbonate (C.sub.4H.sub.5)(OH).sub.1.

[0166] In some embodiments, the hardener has a nitrogen density D in the range from 1 to 15 mmol/g. The mass-specific, polymerization-capable molar nitrogen density D used here is defined by the unit 10.sup.−3 mol/g (corresponding to one thousandth of a mole per gram), which indicates the content of nitrogen atoms having nonaromatic and simultaneously non-binding electron pairs per molecule and function as anionic polymerization initiators.

[0167] In some embodiments, in the hardener, compounds of the following structure types XI to XIV may be present on their own or as any desired mixtures:

##STR00013##

[0168] where R1, R2 and R3=methyl, ethyl, propyl, isopropyl, butyl, isobutyl, benzyl, phenyl, and x=1 to 12, and n=1 to 4.

[0169] A derivative in the present context is understood to mean any component obtainable by reaction of the parent compound, i.e. compounds whose molecules contain another atom or another atom group rather than a hydrogen atom or a functional group or in which an atom or atom group has been removed. The chemical and physical properties of derivatives are often no longer even similar at all to those of the parent compounds but may be similar. The preparation of a chemical derivative is called derivatization.

[0170] In some embodiments, the curing catalyst is present in the solid insulation material in an amount of less than 25% by weight, for example from 0.001% by weight to 15% by weight, or in the range from 0.01% by weight to 10% by weight, or even from 0.1% by weight to 5% by weight, and so gelation times of several hours are achievable.

[0171] In some embodiments, the potting compound formed from an aliphatic and/or cycloaliphatic epoxy resin reacts with a hardener comprising a compound having the structure I within a gelation time of 0.5 h to 48 h, or of 0.5 h to 24 h, and/or of 0.5 h to 16 h under reduced pressure and at encapsulation temperature.

[0172] The potting compound and the insulation material producible therefrom may contain one or more epoxidized reactive diluents, i.e. aromatic and/or aliphatic, short- to long-chain and/or cyclic glycidyl ethers; cyclic reactive diluents such as ethylene carbonate, propylene carbonate, butylene carbonate, glycerol carbonate, glycolic and/or epoxidized polypropylene glycols. The potting compound may contain fillers and/or filler combinations. For example, it is possible to employ microscale fillers composed of quartz flour, boron nitride, fused silica, alumina, wollastonite or aluminum oxide trihydrate. For example, it is possible to employ semiconductive microscale and/or nanoscale fillers or filler combinations or doped fillers or filler combinations.

[0173] The potting compound may include conventional flame retardants and/or flame retardant combinations, and any other additives. In some embodiments, the homopolymerization is effected anionically.

[0174] In some embodiments, the curing catalyst initiates the polymerization of the potting resin at encapsulation temperatures in the range from 20° C. to 150° C., or from 40° C. to 90° C., and/or from 55° C. to 80° C.

[0175] Some embodiments include the curing of a potting compound of cycloaliphatic ECC, i.e. diepoxide 3,4-epoxycyclohexylmethyl 3′,4′-epoxycyclohexanecarboxylate, with 5% by weight of DBN, i.e. 1,5-diazabicyclo[4.3.0]non-5-ene. As a test, the curing was first conducted at 145° C. for 10 h. It was possible to produce a clear, solid and faultless shaped body. According to Gelnorm®, the gelation times were determined as shown in FIG. 1. For this purpose, temperature-dependent gel times were determined at 70° C. to 90° C. with 1% to 10% by weight of DBN in ECC.

[0176] The molding material cured in this way with about 5% by weight of DBM in ECC was examined by means of dynamic differential calorimetry (10 K/min, in nitrogen atmosphere, TA DSC Q100), and two glass transition ranges can be detected. For instance, a well pronounced first glass transition is found at about 60° C., and a less pronounced glass transition at about 153° C., as shown in FIG. 2. It can therefore be assumed that two homo-polymerization stages exist in the network, which cause the toughness of the molding material. An adapted hardness profile, for example longer times and/or higher temperatures, move the glass transition ratio in favor of the higher glass transition.

[0177] FIG. 2 shows the glass transitions in DBN (5% by weight) in ECC molding material after 10 h at 145° C.

[0178] To detect the homopolymerization of ECC by means of DBN, a differential calorimetry analysis of the anionically initiated homopolymerization of the potting compound composed of ECC with DBN as hardener was conducted, with DBN present in the ECC at 7.5% by weight. DBN was stirred into ECC and heated up in flanged crucibles at a heating rate of 10 K/min in a DSC under a nitrogen atmosphere. The graph is shown in FIG. 3. With a reaction enthalpy of more than 650 J/g and an exothermic peak of about 157° C., the homopolymerization of ECC proceeds similarly in terms of mechanism to cationic homopolymerization initiated by superacids.

[0179] The differential calorimetry analysis of the anionically initiated homopolymerization of ECC with DBN as catalyst which is shown in FIG. 3 demonstrates the anionic curing.

[0180] The mixture of 5% DBN in ECC (here in the form of CY179 from Huntsman) thus gives rise to a brittle molding material. FIG. 4 shows the Tg characteristic of the ECC cured with 5% DBN. This is entirely new in the technical field and surprising because anionic polymerization by DBN of sterically hindered ECC was hitherto considered to be impossible.

[0181] Since the focus is on anhydride-free polymerization, all that remains in reality is what is called “homopolymerization”, for example of ECC, i.e. the intercrosslinking of the ECC monomer to give a polymeric material. At the same time, the catalyst disclosed here for the first time is less costly, readily available and less sensitive to moisture and light than the superacids customary to date. The resulting molding material is simultaneously significantly less hydrolysis-sensitive owing to its network structure.

[0182] Some embodiments include a potting compound with a hardener component by means of which anionically initiated homopolymerization of sterically hindered epoxy resins, which was considered to be unfeasible according to prior art to date, is enabled. For this purpose, what are called superbases having a pKB greater than 23 are used.