Polyisocyanurate materials as electrical potting materials

Abstract

The invention relates to a potting compound which cures to form a polyisocyanurate plastic, the production of the potting compound and the use of the potting compound for producing electrical components.

Description

[0001] The invention relates to a potting compound which cures to form a polyisocyanurate plastic, the production of the potting compound and the use of the potting compound for producing electrical components.

[0002] Due to their good insulating properties, plastics are often used to embed electrical components to protect them, for example, from contamination, moisture or contact. The prior art describes the use of epoxies, polyurethanes and silicones for this purpose.

[0003] However, the plastics mentioned above are usually synthesized from two components. Here, the mixing ratio of the two components must be carefully considered in order to achieve the best quality.

[0004] Polyurethane potting compounds are usually based on polymerized methylene di(phenyl diisocyanate) (MDI) and castor oil. MDI has an inherently low viscosity of approximately 200 mPas, which allows the incorporation of high filler contents. This is desirable for flame retardant reasons and due to the high cost of the reactants.

[0005] Two-component reaction mixtures also generally have a short pot life. There is therefore a need for casting resins which do not have the above-mentioned disadvantages.

[0006] Plastics obtainable by crosslinking isocyanate groups with each other are in principle known in the prior art (WO 2015 / 166983; WO 2016 / 170059; European Polymer Journal (1980) 16: 147-148). WO 2017 / 191175 discloses composite materials containing such plastics as a matrix.

[0007] US 2015 / 0344726 describes reaction mixtures with a high NCO / OH ratio and a high filler content. However, these mixtures also contain more than 20% by weight of organic solvents and are therefore suitable for producing coatings but not for producing moldings.

[0008] WO 2014 / 147072 describes a reaction mixture with a high filler content based on bisphenol A diglycidyl ether and diphenylmethane diisocyanate, ie an aromatic polyisocyanate. The crosslinking of the reaction mixture is not achieved by forming isocyanurate groups, but by reacting epoxy groups with isocyanate groups to form oxazolidinones.

[0009] In the present study, it has surprisingly been found that the electrical properties of polyisocyanurate plastics, in particular the dielectric constant and the loss factor, are advantageous for use in electrical potting compounds. When suitable fillers are used, the reaction mixture simultaneously has a sufficiently low viscosity to enable the production of electrical potting compounds.

[0010] In a first embodiment, the present invention therefore provides a casting resin having a molar ratio of isocyanate groups to isocyanate-reactive groups of at least 3:1 and a solvent content of up to 10% by weight, wherein the casting resin contains

[0011] (i) at least one monomeric or oligomeric polyisocyanate A having an isocyanate content of at least 15% by weight;

[0012] (ii) at least one inorganic filler B containing silicon oxide units, which has an oil value of at most 25 g / 100 g and a Mohs hardness of at least 4, determined in accordance with DIN EN ISO 787-5 (October 1995); and

[0013] (iii) at least one trimerization catalyst C.

[0014] "Casting resins" are reactive resins which contain the components defined above and which cure to form polyisocyanurate composite materials. Here, the polyisocyanurate plastic obtained from the polyisocyanate A forms a polymer matrix in which the inorganic filler B is embedded. The term "casting resin" therefore characterizes a reaction mixture in which the components defined above are present in reactive and mixed form so that the polyisocyanate A can be crosslinked by means of a trimerization catalyst C. The casting resins according to the invention are advantageously used to embed electrical components, i.e. as electrical potting materials. Electrical components are completely or partially embedded in the casting resin according to the invention for protection against environmental influences, protection against contact, electrical insulation or mechanical stabilization.

[0015] By curing the casting resin, a polyisocyanurate material is obtained. This is a composite material consisting of polyisocyanurate plastic as a matrix material and an inorganic filler B. It further contains residues of a trimerization catalyst C and optional additives such as UV stabilizers, flow aids or pigments.

[0016] The electrical components are preferably selected from transformers, insulators, capacitors, semiconductors, sleeves for protecting cable joints and underground cable branches.

[0017] Polyisocyanurate plastic

[0018] The term "polyisocyanurate plastics" describes plastics obtained by crosslinking isocyanate groups with one another. This is achieved when the casting resin contains a catalyst C suitable for such crosslinking and at the same time has a high molar ratio of isocyanate groups to isocyanate-reactive groups. As a result, very primarily only other isocyanate groups serve as reaction partners for the isocyanate groups. The term "isocyanate-reactive groups" is understood in the present application to mean epoxy, hydroxyl, amino and thiol groups.

[0019] The molar ratio of isocyanate groups to isocyanate-reactive groups in the casting resin is preferably at least 3:1, preferably at least 5:1, even more preferably at least 10:1, most preferably at least 20:1.

[0020] In the production of moldings, high solvent contents in the reaction mixture are disadvantageous because the solvent evaporates and leaves voids or cracks in the molding. The casting resin according to the invention therefore contains up to 10% by weight, preferably up to 5% by weight, more preferably up to 2% by weight of solvent. The term "solvent" is understood to mean all organic solvents and water that are liquid at room temperature. Chemical compounds having at least one isocyanate-reactive group as defined above or at least one isocyanate group are not solvents in the present patent application, since they can crosslink with the polyisocyanate A via the functional groups involved.

[0021] In the reaction of the reaction mixture to provide the polyisocyanurate plastic, at least 50 mol %, preferably at least 60 mol %, particularly preferably at least 70 mol %, in particular at least 80 mol %, very particularly preferably 90 mol % of the free isocyanate groups present in the polyisocyanate A are converted into isocyanurate structural units. The final polyisocyanurate plastic thus incorporates a corresponding proportion of the nitrogen originally contained in the polyisocyanate A into the isocyanurate structure. However, side reactions often occur, especially those that produce uretdione, allophanate and / or iminooxadiazinedione structures, and can even be used in a controlled manner to advantageously influence, for example, the glass transition temperature (Tg) of the resulting polyisocyanurate plastic.

[0022] Due to the significant molar excess of isocyanate groups relative to isocyanate-reactive groups in the reaction mixture according to the invention, up to 50 mol %, preferably up to 30 mol %, particularly preferably up to 10 mol %, very particularly preferably up to 5 mol % and in particular up to 3 mol % of the reactive isocyanate groups contained in the reaction mixture will be present as urethane and / or allophanate groups in the polyisocyanurate plastic.

[0023] Since inorganic fillers, as is customary in polyurethane chemistry, are permitted to have only low moisture contents, they are inert with respect to isocyanate groups and can be disregarded in the abovementioned calculations.

[0024] Polyisocyanate A

[0025] The term "polyisocyanate" as used herein is a collective term for compounds containing two or more isocyanate groups in the molecule (which is understood by those skilled in the art to refer to free isocyanate groups of the general structure -N=C=O). The simplest and most important representatives of these polyisocyanates are diisocyanates. These have the general structure O=C=N-R-N=C=O, where R generally represents an aliphatic, alicyclic and / or aromatic group. In the present application, the term "polyisocyanate A" refers to the entirety of all compounds having an average of at least two isocyanate groups per molecule contained in the reaction mixture. Polyisocyanate A can therefore consist of a single polyisocyanate. However, it can also be a mixture of a plurality of different polyisocyanates. In the embodiments defined below, polyisocyanate A may also contain admixtures of isocyanates having an average functionality of less than 2.

[0026] Due to the high functionality (≥ 2 isocyanate groups per molecule), a wide variety of polymers (e.g. polyurethanes, polyureas and polyisocyanurates) and low molecular weight compounds (e.g. those with uretdione, isocyanurate, allophanate, biuret, iminooxadiazinedione and / or oxadiazinetriaone structures) can be produced from polyisocyanates.

[0027] In the present application, the term "polyisocyanate" refers equally to monomeric and / or oligomeric polyisocyanates. However, in order to understand many aspects of the present invention, it is important to distinguish between monomeric diisocyanates and oligomeric polyisocyanates. When "oligomeric polyisocyanate" is mentioned in the present application, this refers to a polyisocyanate formed from at least two monomeric diisocyanate molecules, i.e. a compound that constitutes or contains a reaction product formed from at least two monomeric diisocyanate molecules.

[0028] The manufacture of oligomeric polyisocyanates from monomeric diisocyanates is also referred to herein as modification of monomeric diisocyanates. As used herein, such "modification" refers to the reaction of monomeric diisocyanates to produce oligomeric polyisocyanates having uretdione, isocyanurate, allophanate, biuret, iminooxadiazinedione and / or oxadiazinedione structures.

[0029] Thus, for example, hexamethylene diisocyanate (HDI) is a "monomeric diisocyanate" because it contains two isocyanate groups and is not the reaction product of at least two polyisocyanate molecules:

[0030] .

[0031] In contrast, the reaction products of at least two HDI molecules which always still have at least two isocyanate groups are "oligomeric polyisocyanates" in the context of the present invention. Starting from monomeric HDI, representatives of such "oligomeric polyisocyanates" are, for example, HDI isocyanurate and HDI biuret, each of which is composed of three monomeric HDI molecules:

[0032] .

[0033] According to the invention, the proportion by weight of isocyanate groups, based on the total amount of polyisocyanate A, is at least 15% by weight.

[0034] In principle, monomeric and oligomeric polyisocyanates are equally suitable for the reaction mixture according to the invention. Polyisocyanate A can therefore consist essentially of monomeric polyisocyanates or essentially of oligomeric polyisocyanates. However, it can also contain oligomeric and monomeric polyisocyanates in any mixing ratio.

[0035] In a preferred embodiment of the present invention, the polyisocyanate A used as reactant is lean in monomer (i.e. lean in monomer diisocyanate) and already contains oligomeric polyisocyanate. The terms "lean in monomer" and "lean in monomer diisocyanate" are used synonymously with respect to polyisocyanate A herein.

[0036] Particularly useful results are obtained when polyisocyanate A has a proportion of monomeric diisocyanates of up to 20% by weight, in particular up to 15% by weight or up to 10% by weight, based in each case on the weight of polyisocyanate A. Preferably, polyisocyanate A has a monomeric diisocyanate content of up to 5% by weight, preferably up to 2.0% by weight, more preferably up to 1.0% by weight, based in each case on the weight of polyisocyanate A. Particularly good results are established when polyisocyanate A is substantially free of monomeric diisocyanates. "Substantially free" here means that the content of monomeric diisocyanates is up to 0.5% by weight, based on the weight of polyisocyanate A.

[0037] In a particularly preferred embodiment of the present invention, polyisocyanate A is composed entirely or to an extent of at least 80, 85, 90, 95, 98, 99 or 99.5% by weight, based in each case on the weight of polyisocyanate A, of oligomeric polyisocyanates. Preference is given to an oligomeric polyisocyanate content of at least 99% by weight. This content of oligomeric polyisocyanates relates to polyisocyanates A as supplied. That is, the oligomeric polyisocyanates are not formed as intermediates during the process according to the invention, but are already present in the polyisocyanate A used as reactant at the start of the reaction.

[0038] Polyisocyanate compositions which are depleted in monomers or substantially free of monomeric isocyanates can be obtained by carrying out, in each case after the actual modification reaction, at least one further process step for separating off unconverted excess monomeric diisocyanate. This monomer separation can be achieved in a particularly practical manner by methods known per se, preferably by thin-film distillation under high vacuum or by extraction with suitable solvents which are inert toward isocyanate groups, for example aliphatic or cycloaliphatic hydrocarbons, such as pentane, hexane, heptane, cyclopentane or cyclohexane.

[0039] In a preferred embodiment of the invention, the polyisocyanates A are obtained by modification of monomeric diisocyanates and subsequent separation of the unconverted monomers.

[0040] However, in a particular embodiment of the invention, the monomer-poor polyisocyanate A contains a monomeric foreign diisocyanate. In this context, "monomeric foreign diisocyanate" means a monomeric diisocyanate which is different from the oligomeric polyisocyanate contained in the polyisocyanate A which has been used to make it.

[0041] The addition of monomeric external diisocyanates can be advantageous for achieving certain technical effects, such as a certain hardness. Particularly practically interesting results are obtained when the isocyanate A has a proportion of monomeric external diisocyanates of not more than 20% by weight, in particular not more than 15% by weight or not more than 10% by weight, based in each case on the weight of the polyisocyanate A. Preferably, the isocyanate A has a content of monomeric external diisocyanates of not more than 5% by weight, preferably not more than 2.0% by weight, more preferably not more than 1.0% by weight, based in each case on the weight of the polyisocyanate A.

[0042] In another specific embodiment of the method of the present invention, polyisocyanate A contains monomeric monoisocyanates or monomeric isocyanates with an isocyanate functionality greater than 2, i.e. monomeric isocyanates with more than two isocyanate groups per molecule. It has been found that the addition of monomeric monoisocyanates or monomeric isocyanates with an isocyanate functionality greater than 2 is advantageous in order to influence the network density of the coating. When isocyanate A has a ratio of monomeric monoisocyanates or monomeric isocyanates with an isocyanate functionality greater than 20% by weight, especially up to 15% by weight or up to 10% by weight in polyisocyanate A, particularly practical results are established. Preferably, polyisocyanate A has a content of monomeric monoisocyanates or monomeric isocyanates with an isocyanate functionality greater than 2 of up to 5% by weight, preferably up to 2.0% by weight, more preferably up to 1.0% by weight, based on the weight of isocyanate A in each case. Preferably, no monomeric monoisocyanates or monomeric isocyanates having an isocyanate functionality of greater than 2 are subsequently used in the trimerization reaction according to the invention.

[0043] According to the invention, the oligomeric polyisocyanate may contain in particular uretdione, isocyanurate, allophanate, biuret, iminooxadiazinedione and / or oxadiazinetrione structures. In one embodiment of the invention, the oligomeric polyisocyanate has at least one of the following oligomeric structure types or a mixture thereof:

[0044] .

[0045] In a preferred embodiment of the present invention, polyisocyanates A are used whose proportion of isocyanurate structures is at least 50 mol %, preferably at least 60 mol %, more preferably at least 70 mol %, even more preferably at least 80 mol %, even more preferably at least 90 mol % and particularly preferably at least 95 mol %, based on the sum of the oligomeric structures selected from uretdione, isocyanurate, allophanate, biuret, iminooxadiazinedione and oxadiazinetriaone structures present in the polyisocyanate A.

[0046] In a further preferred embodiment of the invention, polyisocyanates A are used in the process according to the invention which contain not only isocyanurate structures but also at least one further oligomeric polyisocyanate having uretdione, biuret, allophanate, iminooxadiazinedione and oxadiazinetriane structures and mixtures thereof.

[0047] The proportion of uretdione, isocyanurate, allophanate, biuret, iminooxadiazinedione and / or oxadiazinetrione structures in the polyisocyanate A can be determined, for example, by NMR spectroscopy. 13 C NMR spectroscopy (preferably in proton decoupled form), since the oligomeric structures mentioned give rise to characteristic signals.

[0048] Irrespective of the basic oligomeric structure (uretdione, isocyanurate, allophanate, biuret, iminooxadiazinedione and / or oxadiazinetrione structure), the oligomeric polyisocyanates A used in the process according to the invention preferably have an (average) NCO functionality of 2.0 to 5.0, preferably 2.3 to 4.5.

[0049] Particularly practically interesting results are achieved when the polyisocyanates A used according to the invention have an isocyanate group content of 8.0% to 28.0% by weight, preferably 14.0% to 25.0% by weight, based in each case on the weight of the polyisocyanate A.

[0050] Processes for the production of oligomeric polyisocyanates having a uretdione, isocyanurate, allophanate, biuret, iminooxadiazinedione and / or oxadiazinetriaone structure for polyisocyanates A according to the invention are described, for example, in J. Prakt. Chem. 336 (1994) 185-200, DE-A 1 670 666, DE-A 1 954 093, DE-A 2 414 413, DE-A 2 452 532, DE-A 2 641 380, DE-A 3 700 209, DE-A 3 900 053 and DE-A 3 928 503 or in EP-A 0 336 205, EP-A 0 339 396 and EP-A 0 798 299.

[0051] In an additional or alternative embodiment of the invention, polyisocyanate A is defined as containing oligomeric polyisocyanates which have been obtained from monomeric diisocyanates (regardless of the nature of the modification reaction used) with a degree of oligomerization of 5% to 45%, preferably 10% to 40%, particularly preferably 15% to 30%. "Degree of oligomerization" is understood here to mean the percentage of isocyanate groups initially present in the starting mixture which are consumed during the production process to form urethane, uretdione, isocyanurate, allophanate, biuret, iminooxadiazinedione and / or oxadiazinetriaone structures.

[0052] Suitable polyisocyanates for producing the polyisocyanates A used in the process according to the invention and the monomeric and / or oligomeric polyisocyanates contained therein are any polyisocyanates which can be obtained in various ways, for example by phosgenation in the liquid phase or the gas phase or by a phosgene-free route, for example by thermal urethane cleavage. Particularly good results are achieved when the polyisocyanates are monomeric diisocyanates. Preferred monomeric diisocyanates are those having 140 to 400 g / mol molecular weight, those with aliphatically, cycloaliphatically, araliphatically and / or aromatically bonded isocyanate groups, for example 1,4-butane diisocyanate (BDI), 1,5-pentane diisocyanate (PDI), 1,6-hexane diisocyanate (HDI), 2-methyl-1,5-pentane diisocyanate, 1,5-diisocyanato-2,2-dimethylpentane, 2,2,4- or 2,4,4-trimethyl-1,6-hexane diisocyanate, 1,10-decane diisocyanate, 1,3- and 1,4-cyclohexane diisocyanate, 1,4 -diisocyanato-3,3,5-trimethylcyclohexane, 1,3-diisocyanato-2-methylcyclohexane, 1,3-diisocyanato-4-methylcyclohexane, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate; IPDI), 1-isocyanato-1-methyl-4(3)-isocyanatomethylcyclohexane, 2,4'- and 4,4'-dicyclohexylmethane diisocyanate (H12MDI), 1,3- and 1,4-bis(isocyanatomethyl)cyclohexane, bis(isocyanatomethyl)cyclohexane 4,4'-diisocyanato-3,3'-dimethyldicyclohexylmethane, 4,4'-diisocyanato-3,3',5,5'-tetramethyldicyclohexylmethane, 4,4'-diisocyanato-1,1'-di(cyclohexyl), 4,4'-diisocyanato-3,3'-dimethyl-1,1'-di(cyclohexyl), 4,4'-diisocyanato-2,2',5,5'-tetramethyl-1,1'-di(cyclohexyl), 1,8-diisocyanato-p-menthane, 1,3-adamantane diisocyanato esters, 1,3-dimethyl-5,7-adamantane diisocyanate, 1,3- and 1,4-bis(isocyanatomethyl)benzene (xylylene diisocyanate; XDI), 1,3- and 1,4-bis(1-isocyanato-1-methylethyl)benzene (TMXDI) and bis(4-(1-isocyanato-1-methylethyl)phenyl)carbonate, 2,4- and 2,6-toluene diisocyanate (TDI), 2,4'- and 4,4'-diphenylmethane diisocyanate (MDI), 1,5-naphthalene diisocyanate and any mixtures of these diisocyanates. Other diisocyanates that are also suitable can be found, for example, in Justus Liebigs Annalen der Chemie, volume 562 (1949) pages 75-136.

[0053] Suitable monomeric monoisocyanates which can be optionally used in isocyanate component A are, for example, n-butyl isocyanate, n-pentyl isocyanate, n-hexyl isocyanate, n-heptyl isocyanate, n-octyl isocyanate, undecyl isocyanate, dodecyl isocyanate, tetradecyl isocyanate, cetyl isocyanate, octadecyl isocyanate, cyclopentyl isocyanate, cyclohexyl isocyanate, 3- or 4-methylcyclohexyl isocyanate or any mixtures of these monoisocyanates. An example of a monomeric isocyanate having an isocyanate functionality of greater than 2 which can be optionally added to polyisocyanate component A is 4-isocyanatomethyloctane 1,8-diisocyanate (nonane triisocyanate; TIN).

[0054] In one embodiment of the invention, polyisocyanate A contains up to 30% by weight, in particular up to 20% by weight, up to 15% by weight, up to 10% by weight, up to 5% by weight or up to 1% by weight of aromatic polyisocyanates, based in each case on the weight of polyisocyanate A. “Aromatic polyisocyanate” as used herein is understood to mean a polyisocyanate having at least one aromatically bonded isocyanate group.

[0055] Aromatically bonded isocyanate groups are understood to mean isocyanate groups which are bonded to an aromatic hydrocarbon radical.

[0056] In a preferred embodiment of the process according to the invention, polyisocyanates A are used which have exclusively aliphatically and / or cycloaliphatically bonded isocyanate groups.

[0057] Aliphatic and cycloaliphatic isocyanate groups are understood to mean isocyanate groups bonded to aliphatic and cycloaliphatic hydrocarbon radicals, respectively. In a further preferred embodiment of the process according to the invention, a polyisocyanate A is used which consists of or comprises one or more oligomeric polyisocyanates, wherein the one or more oligomeric polyisocyanates have exclusively aliphatically and / or cycloaliphatically bonded isocyanate groups.

[0058] In a further embodiment of the invention, polyisocyanate A consists to an extent of at least 70, 80, 85, 90, 95, 98 or 99% by weight, based in each case on the weight of polyisocyanate A, of polyisocyanates having exclusively aliphatically and / or cycloaliphatically bonded isocyanate groups. Practical experiments have shown that particularly good results can be achieved with polyisocyanates A in which the oligomeric polyisocyanates contained therein have exclusively aliphatically and / or cycloaliphatically bonded isocyanate groups.

[0059] In a particularly preferred embodiment of the process according to the invention, a polyisocyanate A is used which consists of or contains one or more oligomeric polyisocyanates, wherein the one or more oligomeric polyisocyanates are based on 1,4-butane diisocyanate (BDI), 1,5-pentane diisocyanate (PDI), 1,6-hexane diisocyanate (HDI), isophorone diisocyanate (IPDI) or 4,4'-dicyclohexylmethane diisocyanate (H12MDI) or mixtures thereof.

[0060] Inorganic filler B

[0061] In order to achieve good mechanical properties of the final component, the inorganic filler B has a Mohs hardness of at least 4.0, preferably at least 5.0, more preferably at least 5.5. According to the invention, fillers containing silicon oxide units are preferred. These are especially silicates and quartz. It is particularly preferred that filler B is quartz or feldspar.

[0062] High filler contents are desirable in principle in order to keep material costs low and to achieve good flame retardancy. However, high filler contents have the disadvantage that they increase the viscosity of the casting resin. This is less of a problem when polymeric MDI (pMDI) is used as a synthesis component for polyurethanes, since pMDI has a viscosity of approximately 90-200 mPas. When pMDI is to be replaced by aliphatic isocyanates, the viscosity of the casting resin reaches the processing critical limit more quickly, since oligomeric aliphatic isocyanates generally have a viscosity of 1500 mPas or more. Special fillers must therefore be selected here which, even at high filler contents in combination with aliphatic isocyanates, lead to low viscosities of the casting resin.

[0063] The critical parameter here is the oil number. The examples show that when the oil number of the inorganic filler B is at most 25 g / 100 g, a viscosity of 110 Pas is not exceeded after the reaction mixture has been stored at 60° C. for 1 hour. Comparative Examples V6 and V7 show that high viscosities are already achieved or such that it is no longer possible to produce a liquid reaction mixture using fillers which are otherwise in accordance with the invention but whose oil numbers are slightly higher than the values ​​in accordance with the invention. Furthermore, a direct comparison of V4 with E10 shows that fillers which do not contain silicon oxide units have a 40% higher viscosity after storage at 60° C. for 1 hour even at very low oil numbers (15 g / 100 g in V4 compared with 21 g / 100 g in E10).

[0064] The inorganic filler B therefore has an oil value, determined in accordance with DIN EN ISO 787-5 (October 1995), of at most 25 g / 100 g, preferably at most 22 g / 100 g, more preferably at most 20 g / 100 g.

[0065] The fillers may be provided with conventional coatings, for example fatty acids, silanes or titanates.

[0066] The casting resin preferably consists of the inorganic filler B to an extent of 30 to 90 wt %, preferably 40 to 80 wt %, more preferably 50 to 80 wt %, particularly preferably 50 to 65 wt %.

[0067] It has proven to be particularly advantageous that, for highly filled materials, in particular materials with a filler content of up to 65% by weight, the casting resin still has a viscosity that is sufficiently low for processing. The casting resin according to the invention is therefore preferably characterized in that, when using up to 65% by weight of inorganic fillers according to the invention with an oil value of up to 25 g / 100 g determined according to DIN EN ISO 787-5 (October 1995), the casting resin has a viscosity of up to 200 Pas, preferably up to 150 Pas at 60° C. and does not exceed this pot life even after storage at this temperature for at least 1 hour. The viscosity was determined using an MCR301 Rheometer from Anton Paar. A plate / plate system PP25 with a Peltier heating C-PTD200 was used at a frequency of f = 1 Hz and an amplitude of γ = 5%.

[0068] In order to comply with the parameters mentioned in the previous paragraph, it is advantageous if the polyisocyanate A has a viscosity of at most 20 000 mPas, preferably at most 10 000 mPas, more preferably at most 5000 mPas at 25° C. The viscosity is preferably at least 500 mPas.

[0069] Trimerization Catalyst C

[0070] The trimerization catalyst C may consist of one or a mixture of different catalyst types, but contains at least one catalyst which causes the trimerization of isocyanate groups to isocyanurates or iminooxadiazinediones.

[0071] Suitable catalysts for the process according to the invention are, for example, simple tertiary amines, such as triethylamine, tributylamine, N,N-dimethylaniline, N-ethylpiperidine or N,N'-dimethylpiperazine. Suitable catalysts are also the tertiary hydroxyalkylamines described in GB 2 221 465, such as triethanolamine, N-methyldiethanolamine, dimethylethanolamine, N-isopropyldiethanolamine and 1-(2-hydroxyethyl)pyrrolidine, or the catalyst systems known from GB 2 222 161 consisting of mixtures of tertiary bicyclic amines, such as DBU, with simple low molecular weight aliphatic alcohols.

[0072] Many different metal compounds are likewise suitable as trimerization catalysts for use in the process of the invention. Suitable examples are the octoates and naphthenates of manganese, iron, cobalt, nickel, copper, zinc, zirconium, cerium or lead or mixtures thereof with lithium, sodium, potassium, calcium or barium acetates, described as catalysts in DE-A 3 240 613, the sodium and potassium salts of linear or branched alkanecarboxylic acids having up to 10 carbon atoms, such as propionic acid, butyric acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid and undecanoic acid, known from DE-A 3 219 608, the alkali metal or alkaline earth metal salts of aliphatic, cycloaliphatic or aromatic mono- and polycarboxylic acids having 2 to 20 carbon atoms, such as sodium or potassium benzoate, known from EP-A 0 100 129, the alkali metal phenates, such as sodium or potassium phenate, known from GB-PS 1 391 066 and GB-PS 1 386 399, the alkali metal phenates, such as sodium or potassium phenate, known from GB 809 90. 809, alkali metal salts of enolizable compounds and metal salts of weak aliphatic or cycloaliphatic carboxylic acids, such as sodium methoxide, sodium acetate, potassium acetate, sodium acetoacetate, lead 2-ethylhexanoate and lead naphthenate, basic alkali metal compounds complexed with crown ethers or polyether alcohols, such as complexed sodium or potassium carboxylates, known from EP-A 0 056 158 and EP-A 0 056 159, potassium pyrrolidone salts known from EP-A 0 033 581, mononuclear or polynuclear complexes of titanium, zirconium and / or hafnium, such as tetra-n-butoxyzirconium, zirconium tetra-2-ethylhexanoate and zirconium tetra-2-ethylhexanolate, and European Polymer Journal, Vol. 16, pp. 147-148. (1979), such as dibutyltin dichloride, diphenyltin dichloride, triphenyltin anol, tributyltin acetate, tributyltin oxide, tin dioctoate, dibutyl(dimethoxy)stannane and tributyltin imidazolate.

[0073] Other trimerization catalysts suitable for the process according to the invention are the quaternary ammonium hydroxides known, for example, from DE-A 1 667 309, EP-A 0 013 880 and EP-A 0 047 452, for example tetraethylammonium hydroxide, trimethylbenzylammonium hydroxide, N,N-dimethyl-N-dodecyl-N-(2-hydroxyethyl)ammonium hydroxide, N-(2-hydroxyethyl)-N,N-dimethyl-N-(2,2'-dihydroxymethylbutyl)ammonium hydroxide and 1-(2-hydroxyethyl)-1,4-diazabicyclo[2.2.2]octane hydroxide (ethylene oxide and water added to 1,4-diazabicyclo[2.2.2]octane hydroxide).2] monoaddition products on octane), quaternary hydroxyalkylammonium hydroxides known from EP-A 37 65 or EP-A 10 589, for example N,N,N-trimethyl-N-(2-hydroxyethyl)ammonium hydroxide, trialkylhydroxyalkylammonium carboxylates known from DE-A 2 631 733, EP-A 0 671 426, EP-A 1 599 526 and U.S. Pat. No. 4,789,705, for example N,N,N-trimethyl-N-2-hydroxypropylammonium p-tert-butylbenzoate and N,N,N-trimethyl-N-2-hydroxypropylammonium 2-ethylhexanoate, trialkylhydroxyalkylammonium carboxylates known from EP-A 1 229 016, for example N-benzyl-N,N-dimethyl-N-ethylammonium pivalate, N-benzyl-N,N-dimethyl-N-ethylammonium 2-ethylhexanoate, N-benzyl-N,N,N-tributylammonium 2-ethylhexanoate, N,N-dimethyl-N-ethyl-N-(4-methoxybenzyl)ammonium 2-ethylhexanoate or N,N,N-tributylammonium pivalate, tetrasubstituted ammonium α-hydroxycarboxylates known from WO 2005 / 087828, for example tetramethylammonium lactate, EP-A 0 339 396, EP-A 0 379 914 and EP-A 0 443 167, for example N-methyl-N,N,N-trialkylammonium fluorides with C8-C10-alkyl groups, N,N,N,N-tetra-n-butylammonium fluoride, N,N,N-trimethyl-N-benzylammonium fluoride, tetramethylphosphonium fluoride, tetraethylphosphonium fluoride or tetra-n-butylphosphonium fluoride, quaternary ammonium and phosphonium polyfluorides known from EP-A 0 798 299, EP-A 0 896 009 and EP-A 0 962 455, for example benzyltrimethylammonium polyfluoride, tetraalkylammonium alkyl carbonates known from EP-A 0 668 271 and obtainable by reaction of tertiary amines with dialkyl carbonates, or betaine-structured quaternary aminoalkyl carbonates, known from WO 962 455, for example benzyltrimethylammonium hydrogen polyfluoride. Quaternary ammonium hydrogen carbonates known from 1999 / 023128, for example choline hydrogen carbonate, quaternary ammonium salts known from EP 0 102 482 and obtainable from tertiary amines and alkylating esters of phosphoric acid, for example the reaction products of triethylamine, DABCO or N-methylmorpholine with dimethyl methylphosphonate, or tetrasubstituted ammonium salts of lactams known from WO 2013 / 167404, for example trioctylammonium caprolactam or dodecyltrimethylammonium caprolactam.

[0074] Further trimerization catalysts C which are suitable according to the invention can be found, for example, in JH Saunders and KC Frisch, Polyurethanes Chemistry and Technology, pages 94 ff. (1962) and the literature cited therein.

[0075] Particularly preferred are carboxylates and phenolates with metal or ammonium ions as counterions. Suitable carboxylates are anions of all aliphatic or alicyclic carboxylic acids, preferably those of monocarboxylic acids or polycarboxylic acids having 1 to 20 carbon atoms. Suitable metal ions are derived from alkali metals or alkaline earth metals, manganese, iron, cobalt, nickel, copper, zinc, zirconium, cerium, tin, titanium, hafnium or lead. Preferred alkali metals are lithium, sodium and potassium, particularly preferably sodium and potassium. Preferred alkaline earth metals are magnesium, calcium, strontium and barium.

[0076] Very particular preference is given to the octoates and naphthenates of manganese, iron, cobalt, nickel, copper, zinc, zirconium, cerium or lead or mixtures thereof with lithium, sodium, potassium, calcium or barium acetates as described as catalysts in DE-A 3 240 613.

[0077] Very particular preference is likewise given to sodium or potassium benzoate, the alkali metal phenates known from GB-PS 1 391 066 and GB-PS 1 386399, for example sodium or potassium phenate, and the alkali metal and alkaline earth metal oxides, hydroxides, carbonates, alkoxides and phenoxides known from GB 809 809.

[0078] The trimerization catalyst C preferably contains a polyether. This is particularly preferred when the catalyst contains metal ions. Preferred polyethers are selected from crown ethers, diethylene glycol, polyethylene glycol and polypropylene glycol. It has been found to be particularly useful in the process of the present invention to use a trimerization catalyst C containing polyethylene glycol or a crown ether, more preferably 18-crown ether-6 or 15-crown ether-5 as the polyether. The trimerization catalyst C preferably contains polyethylene glycol with a number average molecular weight of 100 to 1000 g / mol, preferably 300 g / mol to 500 g / mol, in particular 350 g / mol to 450 g / mol.

[0079] Very particular preference is given to combinations of the abovementioned carboxylates and phenoxides of alkali metals or alkaline earth metals with polyethers.

[0080] It has also been found that compounds according to the following formula (I) are particularly well suited as catalysts C

[0081]

[0082] Where R 1 and R 2 are independently selected from the group consisting of hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, branched C5-alkyl, unbranched C5-alkyl, branched C6-alkyl, unbranched C6-alkyl, branched C7-alkyl and unbranched C7-alkyl;

[0083] A is selected from O, S and NR 3 , where R 3is selected from the group consisting of hydrogen, methyl, ethyl, propyl, isopropyl, butyl and isobutyl; and

[0084] B, independent of A, selected from OH, SH, NHR 4 and NH2, where R 4 Selected from methyl, ethyl and propyl.

[0085] In a preferred embodiment, A is NR 3 , where R 3 is selected from the group consisting of hydrogen, methyl, ethyl, propyl, isopropyl, butyl and isobutyl. 3 Preferably it is methyl or ethyl. 3 More preferred is methyl.

[0086] In a first variant of this embodiment, B is OH and R 1 and R 2 are independently selected from hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, branched C5-alkyl, unbranched C5-alkyl, branched C6-alkyl, unbranched C6-alkyl, branched C7-alkyl and unbranched C7-alkyl. 1 and R 2 Preferably, independently of each other, they are methyl or ethyl. 1 and R 2 More preferred is methyl.

[0087] In a second variant of this embodiment, B is SH and R 1 and R 2 are independently selected from hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, branched C5-alkyl, unbranched C5-alkyl, branched C6-alkyl, unbranched C6-alkyl, branched C7-alkyl and unbranched C7-alkyl. 1 and R 2 Preferably, independently of each other, they are methyl or ethyl. 1 and R 2 More preferred is methyl.

[0088] In a third variant of this embodiment, B is NHR 4 And R 1 and R 2 are independently selected from hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, branched C5-alkyl, unbranched C5-alkyl, branched C6-alkyl, unbranched C6-alkyl, branched C7-alkyl and unbranched C7-alkyl. 1 and R 2 Preferably, independently of each other, they are methyl or ethyl. 1 and R 2 More preferably, it is methyl. In this variant, R4 is selected from methyl, ethyl and propyl. R4 is preferably methyl or ethyl.4 More preferred is methyl.

[0089] In a fourth variant of this embodiment, B is NH2 and R 1 and R 2 are independently selected from hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, branched C5-alkyl, unbranched C5-alkyl, branched C6-alkyl, unbranched C6-alkyl, branched C7-alkyl and unbranched C7-alkyl. 1 and R 2 Preferably, independently of each other, they are methyl or ethyl. 1 and R 2 More preferred is methyl.

[0090] In another preferred embodiment, A is oxygen.

[0091] In a first variant of this embodiment, B is OH and R 1 and R 2 are independently selected from hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, branched C5-alkyl, unbranched C5-alkyl, branched C6-alkyl, unbranched C6-alkyl, branched C7-alkyl and unbranched C7-alkyl. 1 and R 2 Preferably, independently of each other, they are methyl or ethyl. 1 and R 2 More preferred is methyl.

[0092] In a second variant of this embodiment, B is SH and R 1 and R 2 are independently selected from hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, branched C5-alkyl, unbranched C5-alkyl, branched C6-alkyl, unbranched C6-alkyl, branched C7-alkyl and unbranched C7-alkyl. 1 and R 2 Preferably, independently of each other, they are methyl or ethyl. 1 and R 2 More preferred is methyl.

[0093] In a third variant of this embodiment, B is NHR 4 And R 1 and R 2 are independently selected from hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, branched C5-alkyl, unbranched C5-alkyl, branched C6-alkyl, unbranched C6-alkyl, branched C7-alkyl and unbranched C7-alkyl. 1 and R 2 Preferably, independently of each other, they are methyl or ethyl. 1 and R 2More preferably, it is methyl. In this variant, R 4 is selected from methyl, ethyl and propyl. 4 Preferably it is methyl or ethyl. 4 More preferred is methyl.

[0094] In a fourth variant of this embodiment, B is NH2 and R 1 and R 2 are independently selected from hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, branched C5-alkyl, unbranched C5-alkyl, branched C6-alkyl, unbranched C6-alkyl, branched C7-alkyl and unbranched C7-alkyl. 1 and R 2 Preferably, independently of each other, they are methyl or ethyl. 1 and R 2 More preferred is methyl.

[0095] In yet another preferred embodiment, A is sulfur.

[0096] In a first variant of this embodiment, B is OH and R 1 and R 2 are independently selected from hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, branched C5-alkyl, unbranched C5-alkyl, branched C6-alkyl, unbranched C6-alkyl, branched C7-alkyl and unbranched C7-alkyl. 1 and R 2 Preferably, independently of each other, they are methyl or ethyl. 1 and R 2 More preferred is methyl.

[0097] In a second variant of this embodiment, B is SH and R 1 and R 2 are independently selected from hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, branched C5-alkyl, unbranched C5-alkyl, branched C6-alkyl, unbranched C6-alkyl, branched C7-alkyl and unbranched C7-alkyl. 1 and R 2 Preferably, independently of each other, they are methyl or ethyl. 1 and R 2 More preferred is methyl.

[0098] In a third variant of this embodiment, B is NHR 4 And R 1 and R 2 are independently selected from hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, branched C5-alkyl, unbranched C5-alkyl, branched C6-alkyl, unbranched C6-alkyl, branched C7-alkyl and unbranched C7-alkyl.1 and R 2 Preferably, independently of each other, they are methyl or ethyl. 1 and R 2 More preferably, it is methyl. In this variant, R 4 is selected from methyl, ethyl and propyl. 4 Preferably it is methyl or ethyl. 4 More preferred is methyl.

[0099] In a fourth variant of this embodiment, B is NH2 and R 1 and R 2 are independently selected from hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, branched C5-alkyl, unbranched C5-alkyl, branched C6-alkyl, unbranched C6-alkyl, branched C7-alkyl and unbranched C7-alkyl. 1 and R 2 Preferably, independently of each other, they are methyl or ethyl. 1 and R 2 More preferred is methyl.

[0100] Also suitable are adducts of compounds of the formula (I) and compounds having at least one isocyanate group.

[0101] The umbrella term "adduct" is understood to mean carbamate adducts, thiocarbamate adducts and urea adducts of compounds of formula (I) with compounds having at least one isocyanate group. Carbamate adducts are particularly preferred. When isocyanates react with the functional group B of the compound defined in formula (I), an adduct according to the invention is formed. When B is a hydroxyl group, a carbamate adduct is formed. When B is a thiol group, a thiocarbamate adduct is formed. When B is NH2 or NHR 4 When urea adduct is formed.

[0102] Further catalysts suitable according to the invention are phosphines of the general formula (II) or mixtures of such phosphines

[0103]

[0104] in

[0105] R1, R2 and R3 are identical or different radicals and are each an alkyl or cycloalkyl radical having up to 10 carbon atoms, preferably an alkyl radical having 2 to 8 carbon atoms or a cycloalkyl radical having 3 to 8 carbon atoms, an aralkyl radical having 7 to 10, preferably 7 carbon atoms or an aryl radical having 6 to 10, preferably 6 carbon atoms, optionally substituted by an alkyl radical having up to 10, preferably 1 to 6 carbon atoms, provided that at most one of the radicals is an aryl radical and at least one of the radicals is an alkyl or cycloalkyl radical, or wherein

[0106] R1 and R2 are aliphatic in nature and, together with the phosphorus atom, are linked to each other to form a heterocyclic ring having 4 to 6 ring members, wherein R3 is an alkyl group having up to 4 carbon atoms.

[0107] Suitable tertiary organic phosphines are, for example, tertiary phosphines with linear aliphatic substituents, such as trimethylphosphine, triethylphosphine, tri-n-propylphosphine, tripropylphosphine, dibutylethylphosphine, tri-n-butylphosphine, triisobutylphosphine, tri-tert-butylphosphine, pentyldimethylphosphine, pentyldiethylphosphine, pentyldipropylphosphine, pentyldibutylphosphine, pentyldihexylphosphine, dipentylmethylphosphine, dipentylethylphosphine, dipentylpropylphosphine, dipentylbutylphosphine, dipentylhexylphosphine, dipentyloctylphosphine, tripentylphosphine, hexyldimethylphosphine, hexyldiethylphosphine, hexyldipropylphosphine, hexyldibutylphosphine, dihexylmethylphosphine, dihexylethylphosphine, dihexylpropylphosphine, dihexylbutylphosphine, trihexylphosphine, trioctylphosphine, tribenzylphosphine, benzyldimethylphosphine, dimethylphenylphosphine or butylphosphacyclopentane.

[0108] Further tertiary organic phosphines suitable for the process according to the invention are the tertiary phosphines having at least one cycloaliphatic group bonded directly to the phosphorus, such as cyclopentyldimethylphosphine, cyclopentyldiethylphosphine, cyclopentyldi-n-propylphosphine, cyclopentyldiisopropylphosphine, cyclopentyldibutylphosphine with any isomeric butyl groups, cyclopentyldihexylphosphine with any isomeric hexyl groups, cyclopentyldioctylphosphine with any isomeric octyl groups, dicyclopentylmethylphosphine, dicyclopentylethylphosphine, dicyclopentyl-n-propylphosphine, dicyclopentylisopropylphosphine, dicyclopentylbutylphosphine with any isomeric butyl groups, dicyclopentylhex ... The invention also includes dicyclopentyloctylphosphine, tricyclopentylphosphine, cyclohexyldimethylphosphine, cyclohexyldiethylphosphine, cyclohexyldi-n-propylphosphine, cyclohexyldiisopropylphosphine, cyclohexyldibutylphosphine with any isomeric butyl groups, cyclohexyldihexylphosphine with any isomeric hexyl groups, cyclohexyldioctylphosphine with any isomeric octyl groups, dicyclohexylmethylphosphine, dicyclohexylethylphosphine, dicyclohexyl-n-propylphosphine, dicyclohexylisopropylphosphine, dicyclohexylbutylphosphine with any isomeric butyl groups, dicyclohexylhexylphosphine with any isomeric hexyl groups, dicyclohexyloctylphosphine with any isomeric octyl groups, and tricyclohexylphosphine.

[0109] Further suitable tertiary organic phosphines for the process according to the invention are tertiary phosphines which are known, for example, from EP 1 982 979 A1 and have one or two tertiary alkyl groups bonded directly to the phosphorus, for example tert-butyl dimethyl phosphine, tert-butyl diethyl phosphine, tert-butyl di-n-propyl phosphine, tert-butyl diisopropyl phosphine, tert-butyl dibutyl phosphine with any isomeric butyl groups as non-tert-butyl groups, tert-butyl dihexyl phosphine with any isomeric hexyl groups but in which at most one of the hexyl groups has a tertiary carbon atom bonded directly to the phosphorus, tert-butyl dioctyl phosphine with any isomeric octyl groups but in which at most one of the octyl groups has a tertiary carbon atom bonded directly to the phosphorus, di-tert-butyl methyl phosphine, di-tert-butyl ethyl phosphine, di-tert-butyl n-propyl phosphine, di-tert-butyl isopropyl phosphine, in which the non-tert-butyl groups may be n-butyl, isobutyl, 2-butyl di-tert-butylbutylphosphine having any isomeric hexyl or cyclobutyl groups, di-tert-butylhexylphosphine having any isomeric hexyl groups which have no tertiary carbon atom directly bonded to phosphorus, di-tert-butyloctylphosphine having any isomeric octyl groups which have no tertiary carbon atom directly bonded to phosphorus, tert-amyldimethylphosphine, tert-amyldiethylphosphine, tert-amyldi-n-propylphosphine, tert-amyldiisopropylphosphine, tert-amyldibutylphosphine having any isomeric butyl groups but at most one of the butyl groups is tert-butyl, tert-amyldihexylphosphine having any isomeric hexyl groups but at most one of the hexyl groups has a tertiary carbon atom directly bonded to phosphorus, tert-amyldioctylphosphine having any isomeric octyl groups but at most one of the octyl groups has a tertiary carbon atom directly bonded to phosphorus dioctyl phosphine, di-tert-amyl ethyl phosphine, di-tert-amyl ethyl phosphine, di-tert-amyl n-propyl phosphine, di-tert-amyl isopropyl phosphine, di-tert-amyl butyl phosphine in which the butyl group can be n-butyl, isobutyl, 2-butyl or cyclobutyl, di-tert-amyl hexyl phosphine with any isomeric hexyl groups that do not have a tertiary carbon atom directly bonded to phosphorus, di-tert-amyl octyl phosphine with any isomeric octyl groups that do not have a tertiary carbon atom directly bonded to phosphorus, adamantyl dimethyl phosphine, adamantyl diethyl phosphine, adamantyl di-n-propyl phosphine, adamantyl diisopropyl phosphine, adamantyl dibutyl phosphine with any isomeric butyl groups but in which at most one of the butyl groups has a tertiary carbon atom directly bonded to phosphorus, di-tert-amyl hexyl phosphine with any isomeric octyl groups that do not have a tertiary carbon atom directly bonded to phosphorus, The term "adamantyl dihexylphosphine" refers to adamantyl dihexylphosphine with isomeric hexyl groups but at most one of the hexyl groups has a tertiary carbon atom directly bonded to phosphorus, adamantyl dioctylphosphine with any isomeric octyl groups but at most one of the octyl groups has a tertiary carbon atom directly bonded to phosphorus, diadamantyl methylphosphine, diadamantyl ethylphosphine, diadamantyl n-propylphosphine, diadamantyl isopropylphosphine, diadamantyl butylphosphine in which the butyl group may be n-butyl, isobutyl, 2-butyl or cyclobutyl, diadamantyl hexylphosphine with any isomeric hexyl groups that do not have a tertiary carbon atom directly bonded to phosphorus, and diadamantyl octylphosphine with any isomeric hexyl groups that do not have a tertiary carbon atom directly bonded to phosphorus.

[0110] Preferably, the catalyst contains at least one compound selected from the group consisting of the tertiary phosphines mentioned having linear aliphatic substituents.

[0111] Very particularly preferred phosphine catalysts are tri-n-butylphosphine and / or trioctylphosphine or mixtures thereof.

[0112] Components having a very high hardness can be produced from the potting compound according to the invention.

[0113] The potting compound according to the invention is a one-component system. Unlike a two-component system, the stoichiometric ratio between the two reaction partners does not have to be followed exactly to obtain good results. Slight deviations in the concentration of the catalyst used in the potting compound according to the invention may lead to slight variations in the pot life and curing time, but do not impair the properties of the final material.

[0114] Despite the use of aliphatic polyisocyanates which inherently have a relatively high viscosity, the potting compound exhibits such a low viscosity even at high filler contents that it can be processed without major problems.

[0115] Furthermore, the potting compounds according to the invention have a pot life of less than 1 hour, thereby also simplifying their processing. Here, the potting compounds according to the invention also have a pot life of at least 1 hour even at elevated temperatures. The combination of inherently low viscosity and long pot life at elevated temperatures thus greatly simplifies the processing, in particular the degassing, of the potting compounds according to the invention.

[0116] The potting compound according to the invention also has a lower fire hazard than known polyurethane potting compounds.

[0117] use

[0118] In another embodiment, the present invention provides for the use of a potting compound as defined above in the present application as an electrical potting compound, ie for the production of electrical components.

[0119] The electrical component is preferably selected from transformers, insulators, capacitors, semiconductors, sleeves for protecting cable joints and underground cable branches.

[0120] Even though a few of the above-mentioned electrical components can be used without the protection of an electrical potting compound in certain fields of application, the term "production of an electrical component" also relates to a method of embedding at least a portion of an electrical component in a potting compound according to the invention. In the present application, the final electrical component therefore contains a potting compound according to the invention.

[0121] method

[0122] In yet another embodiment, the present invention is directed to a method of producing an electrical component comprising the steps of

[0123] a) providing a casting resin having a molar ratio of isocyanate groups to isocyanate-reactive groups of at least 3:1 and a solvent content of up to 10% by weight, comprising

[0124] (i) at least one monomeric or oligomeric polyisocyanate A having an isocyanate content of at least 15% by weight;

[0125] (ii) at least one inorganic filler B containing silicon oxide units, which has an oil value of at most 25 g / 100 g and a Mohs hardness of at least 4, determined in accordance with DIN EN ISO 787-5 (October 1995); and

[0126] (iii) at least one trimerization catalyst C;

[0127] b) potting the electrical components which have not yet been embedded with the casting resin provided in method step a);

[0128] c) catalytic trimerization of the casting resin.

[0129] In the present application, “providing” a casting resin is understood to mean only that the casting resin in question is provided at the end of process step a) in such a way that it is suitable for potting and can catalyze trimerization.

[0130] The potting of the electrical components which have not yet been embedded can be carried out by all methods known from the prior art for potting compounds, in particular electrical potting compounds.

[0131] The catalytic trimerization is carried out under reaction conditions such that the selected trimerization catalyst C achieves crosslinking of the isocyanate groups to provide isocyanurate groups. In the case of temperature-sensitive electrical components, an upper temperature limit for the reaction mixture which is not harmful to the components in question is preferably adhered to.

[0132] "Catalytic trimerization" is a process in which the isocyanate groups contained in the polyisocyanate A react with each other or with already existing urethane groups to form at least one structure selected from uretdione, isocyanurate, allophanate, biuret, iminooxadiazinedione and oxadiazinedione structures. The isocyanate groups originally present in the polyisocyanate A are consumed. Through the formation of the above-mentioned groups, the monomeric and oligomeric polyisocyanates contained in the polyisocyanate A are linked to form a polymer network.

[0133] Preferably, the crosslinking of the isocyanate groups contained in the reaction mixture is carried out primarily by trimerization of at least 50 mol %, preferably at least 60 mol %, particularly preferably at least 70 mol %, in particular at least 80 mol %, very particularly preferably 90 mol % of the free isocyanate groups present in the polyisocyanate A to provide isocyanurate structural units. The final polyisocyanurate material thus incorporates a corresponding proportion of the nitrogen originally contained in the polyisocyanate A into the isocyanurate structure. However, side reactions usually occur, in particular those that form uretdione, allophanate and / or iminooxadiazinedione structures, and can even be used specifically to advantageously influence, for example, the glass transition temperature (Tg) of the resulting polyisocyanurate material.

[0134] If lower temperatures do not have to be followed due to temperature sensitive components, the catalytic trimerization is preferably carried out at a temperature of 50 to 200°C, more preferably 80 to 180°C, even more preferably 100 to 150°C.

[0135] During the crosslinking of the isocyanate groups, the above-mentioned temperature is maintained until at least 50 mol %, preferably at least 75 mol %, even more preferably at least 90 mol % of the free isocyanate groups present in the semi-finished product according to the invention at the start of the crosslinking of the isocyanate groups have been consumed. This can be determined by comparing the content of isocyanate groups in the isocyanate component A present at the start of the crosslinking of the isocyanate groups with the content of isocyanate groups in the reaction product, for example by comparing the isocyanate groups at about 2270 cm -1 The intensity of the isocyanate band is used to determine the percentage of isocyanate groups still present.

[0136] In another embodiment, the invention relates to an electrical component made by a method as defined above.

[0137] The polymer matrix formed from the casting resin is preferably characterized by a temperature at which a 5 wt. % mass loss occurs of at least 370°C, preferably at least 400°C, most preferably at least 420°C.

[0138] The following examples are intended to illustrate the present invention only and should not limit the scope of the claims in any way. Example

[0139] Raw materials used

[0140] Isocyanate 1: HDI polyisocyanate containing isocyanurate groups prepared according to Example 11 of EP-A 330 966, except that 2-ethylhexanol was used as catalyst solvent instead of 2-ethyl-1,3-hexanediol. The reaction was terminated at an NCO content of the crude mixture of 42% by weight by adding dibutyl phosphate. Subsequently, unconverted HDI was separated off by thin-film distillation at a temperature of 130° C. and a pressure of 0.2 mbar.

[0141] NCO content: 23.0 wt%

[0142] NCO functionality: 3.2

[0143] Monomer HDI: 0.1 wt%

[0144] Viscosity (23°C): 1200 mPas

[0145] Density (20℃): 1.17 g / cm³.

[0146] Distribution of oligomeric structure types:

[0147] Isocyanurate: 89.7 mol%

[0148] Iminoxadiazinedione 2.5 mol%

[0149] Ureadione 2.7 mol%

[0150] Allophanate: 5.1 mol %.

[0151] Isocyanate 2: is an isocyanate-terminated prepolymer prepared by reaction of a difunctional polypropylene glycol polyether (OH number = 515 mg KOH / g) with excess HDI at a temperature of 80°C. After establishment of a constant NCO content, the reaction is terminated by addition of dibutyl phosphate. Subsequently, unconverted HDI is separated off by thin-film distillation at a temperature of 130°C and a pressure of 0.2 mbar.

[0152] NCO content: 12.5 wt%

[0153] NCO functionality: 2.1

[0154] Monomeric HDI: < 0.5 wt%

[0155] Viscosity (23°C): 4250 mPas

[0156] Density (20℃): 1.10 g / cm³.

[0157] Isocyanate 3: A low viscosity mixture of diphenylmethane 4,4'-diisocyanate (MDI) with isomers and higher functional homologues

[0158] NCO content: 31.5 wt%

[0159] Equivalent weight: 133 g / val

[0160] Viscosity (23°C): 90 mPas

[0161] Density (20℃): 1.23 g / cm³.

[0162] Polyol 1: Linear polypropylene glycol ether polyol made by propoxylation of 1,2-propylene glycol

[0163] Hydroxyl value: 520 mg KOH / g

[0164] Viscosity (25°C): 55 mPas

[0165] Density (25℃): 1.00 g / cm³.

[0166] Polyol 2: Glycerol (1,2,3-propanetriol) was obtained from Calbiochem at 99.0% purity.

[0167] Filler 1: Silbond 126 EST is a quartz filler coated with epoxysilane and obtained from Quarzwerke GmbH. According to the technical data sheet, the filler absorbs 11 g of oil / 100 g of filler (DIN ISO 787-5); the Mohs hardness is 7.

[0168] Filler 2: Microdol 1-KN is a dolomite filler and is obtained from Omya. According to the technical data sheet, the filler absorbs 15 g of oil / 100 g of filler (ISO 787 / 5). According to Wikipedia (retrieved February 2019), the Mohs hardness of dolomite is 3.5-4.

[0169] Filler 3: Unispar PG W13 is a feldspar filler and was obtained from Sibelco Corp. According to the technical data sheet, this filler absorbs 22 g of oil / 100 g of filler (ISO 787 / 5); Mohs hardness is 6.2.

[0170] Filler 4: Unispar PG W20 is a feldspar filler and was obtained from Sibelco Corp. According to the technical data sheet, this filler absorbs 19 g oil / 100 g filler (ISO 787 / 5); Mohs hardness is 6.2.

[0171] Filler 5 Omycarb 2T-AV is a calcium carbonate filler and is available from Omya. According to the technical data sheet, this filler absorbs 16 g of oil / 100 g of filler (ISO 787 / 5). According to Wikipedia (retrieved February 2019), the Mohs hardness of calcium carbonate (limestone) is 3.

[0172] Filler 6 Silbond 800 EST is a quartz filler coated with epoxysilane and is available from Quarzwerke GmbH. According to the technical data sheet, this filler absorbs 26 g of oil / 100 g of filler (ISO 787 / 5).

[0173] Filler 7 Silbond 6000 MST is a cristobalite filler coated with methacrylsilane and is available from Quarzwerke GmbH. According to the technical data sheet, the filler absorbs 27 g of oil / 100 g of filler (ISO 787 / 5).

[0174] Filler 8 Sikron SF 800 is a quartz filler and is available from Quarzwerke GmbH. According to the technical data sheet, this filler absorbs 28 g of oil / 100 g of filler (ISO 787 / 5).

[0175] Filler 9 Chinafill 200 is a kaolin filler and is obtained from Amberger Kaolinwerke Eduard Kick GmbH & Co. KG. According to the technical data sheet, the filler absorbs 46 g of oil / 100 g of filler (ISO 787 / 5). According to Wikipedia (retrieved in February 2019), the Mohs hardness of kaolin is 2.5.

[0176] Filler 10 Silitin Z 86 is a mixture of micronized silica and layered kaolinite and is available from HoffmannMineral GmbH. According to the technical data sheet, the filler absorbs 55 g of oil / 100 g of filler (ISO 787 / 5); the Mohs hardness of the silica part is 7 and the Mohs hardness of the kaolinite part is 2.5.

[0177] Filler 11 Silbond 006 MST is a cristobalite filler coated with methacrylsilane and obtained from Quarzwerke GmbH. According to the technical data sheet, the filler absorbs 21 g of oil / 100 g of filler (ISO 787 / 5); the Mohs hardness is 6.5.

[0178] Before processing, the filler was dried at 80°C for 12 hours with regular stirring.

[0179] Catalyst 1: Desmorapid AP 100 was obtained from Covestro AG.

[0180] Catalyst 2: Trioctylphosphine was obtained from abcr GmbH in a purity of 97%.

[0181] Catalyst 3: was a mixture of potassium acetate,

[18] crown ether-6 and diethylene glycol in a ratio of 1.0:2.7:17.6 (obtained from Sigma-Aldrich in PA quality and used as supplied).

[0182] Catalyst 4: Jeffcat Z-110 was obtained from Huntsman Corporation.

[0183] Determination of electrical properties:

[0184] The electrical properties of the materials were determined using a Keithley Model 8009 instrument operating in accordance with ASTM D 257 (May 2007). The measurements were performed at 25°C.

[0185] Determination of glass transition temperature:

[0186] The glass transition temperature was determined by DSC (differential scanning calorimetry) according to DIN EN 61006 (November 2004) with a Mettler DSC 12E (Mettler Toledo GmbH, Gießen, Germany). Calibration was carried out by the melting start temperatures of indium and lead. 10 mg of substance were weighed into a standard capsule. The measurement was carried out by two heating runs from -50°C to +200°C at a heating rate of 20 K / min and subsequent cooling at a cooling rate of 20 K / min. Cooling was carried out with the aid of liquid nitrogen. The purge gas used was nitrogen. The values ​​shown are in each case based on the evaluation of the second heating curve.

[0187] Determination of mass loss:

[0188] The mass loss was determined by TGA (thermogravimetric analysis) according to DIN EN ISO 11358-1:2014-10. For this purpose, approximately 5.5 mg of the product were heated in a TGA-8000 thermogravimetric analyzer (Perkin-Elmer) in an open platinum crucible from 25° C. to 600° C. under a constant nitrogen flow. The heating rate was 20 K / min. The temperature at which the accumulated mass loss over the measuring time reached 5% by weight was evaluated.

[0189] Determination of processing time:

[0190] To determine the processing time, the two components were mixed and measured in a rheometer at 60° C. for 1 hour. The viscosity values ​​indicated are the values ​​determined after exactly 1 hour. An MCR 301 rheometer from Anton Paar was used. A plate / plate system PP 25 with Peltier heating C-PTD 200 was used.

[0191] Measurement configuration: Frequency f = 1 Hz; Amplitude γ = 5%

[0192] T = 60℃, 60 min.

[0193] Determination of Shore hardness:

[0194] The Shore hardness was measured in accordance with DIN 53505 (August 2000) at 23° C. and 50% air humidity using a Zwick 3100 Shore hardness tester (from the company Zwick).

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[0196]

[0197]

[0198]

Claims

1. A casting resin having a molar ratio of isocyanate groups to isocyanate-reactive groups of at least 3:1 and a solvent content of up to 10% by weight, wherein the casting resin contains (i) at least one monomeric or oligomeric polyisocyanate A having an isocyanate content of at least 15% by weight, wherein the polyisocyanate A consists to an extent of at least 70% by weight, based on its total weight, of polyisocyanates having exclusively aliphatically and / or cycloaliphatically bonded isocyanate groups; (ii) at least one inorganic filler B containing silicon oxide units, which has an oil value of at most 25 g / 100 g and a Mohs hardness of at least 4, determined in accordance with DIN EN ISO 787-5, October 1995 edition; and (iii) at least one trimerization catalyst C.

2. The casting resin of claim 1, wherein the inorganic filler has a Mohs hardness of at least 6.

3. A casting resin as claimed in claim 1 or 2, wherein the reaction mixture consists of inorganic filler B to an extent of at least 30% by weight.

4. A casting resin as claimed in claim 3, wherein the reaction mixture consists of inorganic filler B to an extent of at least 65% by weight.

5. A casting resin as claimed in claim 1 or 2, wherein the trimerization catalyst C catalyzes the crosslinking of isocyanate groups to provide isocyanurate groups.

6. A casting resin as claimed in claim 1 or 2, characterized in that At a content of up to 65% by weight of inorganic filler B, the casting resin has a viscosity of at most 150 Pas after storage at 60° C. for 1 hour.

7. Casting resin as claimed in claim 6, wherein the polyisocyanate A has a viscosity at 25°C of at least 500 mPas and at most 20000 mPas.

8. Use of a casting resin as claimed in any one of claims 1 to 7 for producing electrical components.

9. Use as claimed in claim 8, wherein the electrical component is selected from transformers, insulators, capacitors, semiconductors, sleeves for protecting cable joints and underground cable branches.

10. A method for producing an electrical component comprising the steps of a) providing a casting resin as defined in any one of claims 1 to 7; b) potting the electrical components which have not yet been embedded with the casting resin provided in method step a); c) catalytic trimerization of the casting resin.

11. An electrical component manufactured by the method as claimed in claim 10.

12. An electrical assembly as claimed in claim 11, wherein the polymer matrix formed by the cured casting resin is characterized by a temperature at which a 5 weight percent mass loss occurs of at least 370°C.

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