Polyisocyanurate materials as electrical potting compounds
The invention relates to potting compounds which cure to polyisocyanurate plastics, to the production of said potting compounds and to the use of the potting compounds for manufacturing electrical components.
1 . A process for producing an electrical component comprising
a) providing a casting resin;
b) potting a not yet embedded electrical component with the casting resin provided in process step a);
c) catalytically trimerizing isocyanate groups of the casting resin,
the casting resin having a molar ratio of isocyanate groups to isocyanate-reactive groups of at least 3:1 and a solvent content of not more than 10% by weight, wherein the casting resin comprises
(i) at least one monomeric or oligomeric polyisocyanate A having an isocyanate content of at least 15% by weight;
(ii) at least one inorganic filler B containing silicon oxide units having an oil number of not more than 25 g/100 g determined according to DIN EN ISO 787-5 (October 1995) and a Mohs hardness of at least 6; and
iii) at least one trimerization catalyst C,
wherein the casting resin has a viscosity of up to 102 Pas after 1 hour at 60° C.
2 . The process of claim 1 , wherein the polyisocyanate A comprises at least 70% by weight of polyisocyanates having exclusively aliphatically and/or cycloaliphatically bonded isocyanate groups based on a total weight of polyisocyanate A.
3 . The process of claim 1 , comprising at least 30% by weight of the inorganic filler B.
4 . The process of claim 3 , comprising at least 65% by weight of the inorganic filler B.
5 . The process of claim 1 , wherein the trimerization catalyst C catalyzes crosslinking of isocyanate groups to afford isocyanurate groups.
6 . The process of claim 1 , wherein, at a content of up to 65% by weight of the inorganic filler B, said casting resin has a viscosity of not more than 150 Pas after storage for one hour at 60° C.
7 . The process of claim 6 , wherein the polyisocyanate A has a viscosity of at least 500 mPas and not more than 20 000 mPas at 25° C.
8 . A casting resin having a molar ratio of isocyanate groups to isocyanate-reactive groups of at least 3:1 and a solvent content of not more than 10% by weight, wherein the casting resin comprises
(i) at least one monomeric or oligomeric polyisocyanate A having an isocyanate content of at least 15% by weight;
(ii) at least one inorganic filler B containing silicon oxide units having an oil number of not more than 25 g/100 g determined according to DIN EN ISO 787-5 (October 1995) and a Mohs hardness of at least 6; and
(iii) at least one trimerization catalyst C,
wherein the casting resin has a viscosity of up to 102 Pas after 1 hour at 60° C.
9 . An electrical component produced by the process as claimed in claim 1 .
10 . The electrical component as claimed in claim 9 , wherein the polymer matrix formed by the cured casting resin is characterized in that a temperature at which 5% by weight of mass loss occurs is at least 370° C.
11 . The electrical component as claimed in claim 9 , wherein the electrical component is a transformer, insulator, capacitor, semiconductor, junction sleeve for protecting cable connections, or an underground cable branch tee.