Method for variably adjusting the electrical insulating properties of varistor-containing materials
The present invention relates to a process for the variable adjustment of the electrical insulation properties of varistor-containing composite materials with the aid of defined filler mixtures, to the use of such filler mixtures, and to composite materials having resistive and capacitive field-control properties comprising filler mixtures of this type.
1 . A process for the variable adjustment of the electrical insulation properties of varistor-containing composite materials, comprising providing one or more mass unit(s) of a dielectric polymer material and adding a particulate microvaristor filler A having an average particle size d 50 of from 1 to 150 μm and a further particulate filler B in a predefined total mass A+B to each of the one or more mass unit(s), where the particulate filler B either has a lower electrical conductivity than the particulate microvaristor filler A or where the particulate filler B is a semiconductive particulate material having a higher electrical conductivity than that of the particulate microvaristor filler A, and where a mass ratio A: B is in the range of from 1:99 to 99:1, and wherein the mass ratio A:B is set differently in different mass units of the polymer material in the total mass A+B, wherein the particulate microvaristor filler A is a filler which consists of support particles and a coating surrounding each of the support particles, where the support particles comprise at least one aluminium compound or silicon compound, and where the coating comprises a titanium dioxide doped with niobium and at least one further element.
2 . The process according to claim 1 , wherein the total mass A+B, expressed in % by weight, is identical in each of the one or more mass unit(s) of the polymer material, wherein the total mass A+B expressed in % by weight is based on the total weight of a mass unit of the dielectric polymer material including the total mass A+B of the particulate fillers A and B.
3 . The process according to claim 2 , wherein the total mass A+B is in the range of from 5 to 35% by weight, based on the total weight of a mass unit of the dielectric polymer material including the total mass A+B of the particulate fillers A and B.
4 . The process according to claim 1 , wherein each mass unit of the dielectric polymer material that comprises the particulate fillers A and B has an E/ρ characteristic line that lies spatially between an E/ρ characteristic line of a mass unit of the same polymer material which only comprises the particulate microvaristor filler A, and the E/ρ characteristic line of a mass unit of the same polymer material which only comprises the particulate filler B.
5 . The process according to claim 1 , wherein the dielectric polymer material comprises one or more silicones, polyurethanes, polyethylenes, epoxides, phenolic resins and/or ethylene-propylene-diene monomers.
6 . The process according to claim 1 , wherein the particulate microvaristor filler A is a filler which consists of support particles and a coating surrounding each of the support particles, where the support particles consist of at least one aluminium compound or silicon compound, and where the coating comprises a titanium dioxide doped with niobium and at least one further element.
7 . The process according to claim 1 , wherein the support particles comprise aluminium oxide, silicon dioxide or an aluminosilicate.
8 . The process according to claim 1 , wherein the support particles consist of aluminium oxide, silicon dioxide, mullite, fly ash, kaolinite, pumice stone or perlite.
9 . The process according to claim 1 , wherein the at least one further element is selected from the group consisting of Mn, Cr, Ce, V, Co, Fe, Zn, Sn, Y, Zr, Ta, Ca, Sr and Ba.
10 . The process according to claim 9 , wherein the at least one further element is selected from the group consisting of Mn, Cr and Ce.
11 . The process according to claim 1 , wherein the particulate microvaristor filler A has an average particle size in the range of from 5 to 50 μm.
12 . The process according to claim 1 , wherein the particulate filler B is the semiconductive particulate material which has a higher electrical conductivity than the particulate microvaristor filler A and has a specific powder resistance in the range of from 10 8 to 10 12 ohm*cm.
13 . The process according to claim 1 , wherein the particulate filler B has a lower electrical conductivity than the particulate microvaristor filler A and has a specific powder resistance in the range of ≥10 14 ohm*cm.
14 . A method for the variable adjustment of the electrical insulation properties of varistor-containing composite materials, the method comprising adding a filler mixture to one or more mass units of a dielectric polymer material, wherein the filler mixture consists of a predefined total mass A+B comprising a particulate microvaristor filler A having an average particle size d 50 of from 1 to 150 μm and a further particulate filler B, where the particulate filler B either has a lower electrical conductivity than the particulate microvaristor filler A or where the particulate filler B is a semiconductive particulate material having a higher electrical conductivity than the particulate microvaristor filler A, and where a mass ratio A:B is in the range of from 1:99 to 99:1 exists in the total mass A+B, and the mass ratio A:B is set identically or differently from one another in each of the one or more mass unit(s);
wherein at least one of the following conditions apply:
the particulate microvaristor filler A is a filler which consists of support particles and a coating surrounding each of the support particles, where the support particles comprise at least one aluminium compound or silicon compound, and where the coating comprises a titanium dioxide doped with niobium and at least one further element;
and/or
the particulate filler B is the semiconductive particulate material which has a higher electrical conductivity than the particulate microvaristor filler A and has a specific powder resistance in the range of from 10 8 to 10 12 ohm*cm.
15 . The method according to claim 14 , wherein the particulate microvaristor filler A is a filler which consists of support particles and a coating surrounding each of the support particles, where the support particles comprise at least one aluminium compound or silicon compound, and where the coating comprises a titanium dioxide doped with niobium and at least one further element.
16 . The method according to claim 14 , wherein the particulate filler B is the semiconductive particulate material which has a higher electrical conductivity than the particulate microvaristor filler A and has a specific powder resistance in the range of from 10 8 to 10 12 ohm*cm.
17 . The method according to claim 15 , wherein the particulate filler B has a lower electrical conductivity than the particulate microvaristor filler A and has a specific powder resistance in the range of ≥10 14 ohm*cm.
18 . A varistor-containing composite material having resistive and capacitive field-control properties, comprising mass units of a dielectric polymer material, a particulate microvaristor filler A having an average particle size d 50 of from 1 to 150 μm and a further particulate filler B in a predefined total mass A+B in each mass unit of the dielectric polymer material, where the particulate filler B has a lower electrical conductivity than the particulate microvaristor filler A or where the particulate filler B is a semiconductive particulate material having a higher conductivity than the particulate microvaristor filler A, and where the same mass ratio A:B exists in each of the mass units of the polymer material that comprise the particulate fillers A+B and the mass ratio A:B is in the range of from 1:99 to 99:1;
wherein at least one of the following conditions apply:
the particulate microvaristor filler A is a filler which consists of support particles and a coating surrounding each of the support particles, where the support particles comprise at least one aluminium compound or silicon compound, and where the coating comprises a titanium dioxide doped with niobium and at least one further element;
and/or
particulate filler B is the semiconductive particulate material which has a higher electrical conductivity than the particulate microvaristor filler A and has a specific powder resistance in the range of from 10 8 to 10 12 ohm*cm.
19 . The varistor-containing composite material according to claim 18 , wherein the total mass A+B in each of the mass units is in the range of from 5 to 35% by weight, based on the total weight of the mass unit of the dielectric polymer material including the total mass A+B of the particulate fillers A and B.
20 . The varistor-containing composite material according to claim 18 , wherein the dielectric polymer material comprises one or more silicones, polyurethanes, polyethylenes, epoxides, phenolic resins or ethylene-propylene-diene monomers.
21 . A process for the variable adjustment of the electrical insulation properties of varistor-containing composite materials, comprising providing one or more mass unit(s) of a dielectric polymer material and adding a particulate microvaristor filler A having an average particle size d 50 of from 1 to 150 μm and a further particulate filler B in a predefined total mass A+B to each of the one or more mass unit(s), where the particulate filler B either has a lower electrical conductivity than the particulate microvaristor filler A or where the particulate filler B is a semiconductive particulate material having a higher electrical conductivity than that of the particulate microvaristor filler A, and where a mass ratio A:B is in the range of from 1:99 to 99:1, and wherein the mass ratio A:B is set differently in different mass units of the polymer material in the total mass A+B, wherein the total mass A+B is in the range of from 5 to 35% by weight, based on the total weight of a mass unit of the dielectric polymer material including the total mass A+B of the particulate fillers A and B.