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EP-4233078-B1 - NON-CURABLE SILICONE COMPOSITION COMPRISING CARBON BLACK

EP4233078B1EP 4233078 B1EP4233078 B1EP 4233078B1EP-4233078-B1

Inventors

  • SAFAROWSKY, Oliver
  • ERDMANN, Olaf
  • HAEUSER, THORSTEN

Dates

Publication Date
20260506
Application Date
20211021

Claims (15)

  1. A process for the manufacture of a non-curable silicone composition comprising carbon black, said process comprises the extrusion of one or more polyorganosiloxanes a1) with one or more carbon blacks d).
  2. A process according the previous claim, wherein the polyorganosiloxanes a1) are selected from polyorganosiloxanes having one or more unsaturated groups, preferably one or more alkenyl groups.
  3. A process according to any of the previous claims, wherein the extrusion is carried out with an extruder, such as a multi screw extruder, preferably a twin-screw extruder, more preferably a co-rotating twin-screw extruder.
  4. A process according to any of the previous claims, wherein the weight ratio of the weight of the one or more polyorganosiloxanes a1) to weight of the one or more carbon blacks d) is from 90:10 to 75:25, preferably from 89 to 11 to 80 to 20.
  5. A non-curable silicone composition obtained by the process as defined by any of the previous claims.
  6. A non-curable silicone composition according to any of the previous claims comprising at least 10, preferably at least 11, still more preferably at least 12 weight percent of one or more carbon blacks d) based on the total weight of the entire silicone composition, and/or comprising from 10 to 25, preferably from 11 to 24, still more preferably from 12 to 23 weight percent of one or more carbon blacks d) based on the total weight of the entire silicone composition.
  7. A non-curable silicone composition according to any of the previous claims, wherein the percentage of the number of particles less than 10 µm is more than 70 %, preferably more than 80 %, still more preferably more than 90 %, and/or the percentage of the number of particles of more than 10 µm is less than 30 %, preferably less than 20 %, still more preferably less than 10 %, still more preferably less than 5 % each as determined by dynamic light scattering, and/or wherein the Dn 50 of the particle size distribution based on the number of particles of the non-curable silicone composition is less than 7 µm, preferably less than 5 µm, and more preferably less than 3 µm as determined by dynamic light scattering, and/or wherein the Dn 90 of the particle size distribution based on the number of particles of the non-curable silicone composition is less than 15 µm, preferably less than 10 µm, more preferably less than 8 µm, and most preferably less than 5 µm as determined by dynamic light scattering.
  8. Use of the non-curable silicone composition according to any of the previous claims for the manufacture of curable silicone compositions, preferably as a masterbatch for incorporation into curable silicone composition, preferably for use in high voltage direct current applications.
  9. Curable silicone composition comprising the non-curable silicone composition according to any of the previous claims, preferably comprising: a) 100 pt.wt. of one or more polyorganosiloxanes a2) having one or more unsaturated groups, preferably one or more alkenyl groups, b) 0 - 100 pt.wt. of a crosslinker component comprising one or more polyorganohydrogensiloxanes, c) 0 - 100 pt.wt. of one or more filler components, comprising one or more reinforcing silicas or resins, d) 0.1 - 3 pt.wt. of one or more carbon blacks, e) a curing catalyst selected from the group consisting of a compound enabling hydrosilylation and an organic peroxide, and f) 0 - 50 pt.wt. of one or more auxiliary additives.
  10. Curable silicone composition according to claim 9, comprising from 0.1 to 2.4 wt-% preferably 0.2 to 2.4 wt-%, more preferably 0.5 to 2.2 wt-%, even more preferred 1.0 to 2.0 wt-%, and even more preferred 1.3 to 1.8 wt-% of one or more carbon blacks d) based on the total weight of the curable composition.
  11. Cured silicone compositions, obtained by curing the curable silicone compositions according to any of the previous claims 9 to 10.
  12. Cured silicone compositions according to claim 11, • having in a Pulsed Electro Acoustic (PEA) charge movement diagram a movement of any charge < 0.2 mm, preferably < 0.3 mm from one or each electrode, and/or • having in a PEA charge movement diagram a movement of the peak max/min of < 0.05 mm, preferably < 0.1 mm from one or each electrode, and/or • wherein after 5h, preferably after 2.5h in the total charge accumulation diagram the increase of the mean charge density until a measuring time of 20 hours is less than 20 %, preferably less than 10% (steady state), and/or • having a maximum mean charge density in the total charge accumulation diagram at or after 20h of < 1.5 C/m 3 , preferably of < 1.25 C/m 3 and most preferably of < 1.0 C/m 3 , wherein the Pulsed Electro Acoustic charge movement diagram is determined by a method wherein - a static polarization phase takes place prior to the generation of an electrical pulse; - an initial electric impulse being a voltage impulse is generated at the point in time t n after start of electrical polarization at constant temperature and a constant field strength and exerts coulomb forces onto the space charge which were moved by the prior electrical polarization and a pressure impulse subsequently; - this impulse spreads through the sample and an AI electrode with known thickness and impedance as an acoustic wave until reaching a piezo membrane which transforms the acoustic signals back to an electric signature; - the Piezo device being the detector in this system is back filled with an absorber material in order to delay possible reflections in a way that these do not interfere with the initial wave signals; - the front end of the sample reaches the piezo foil at t1 while the back end arrives at t2; - after correction of the system response and other factors including calibration, the transformation to space coordinates (1D) gives a pattern with a charge density as a function of place (x), wherein the total charge density (Q) can be calculated with the equation Q avg = 1 d ⋅ ∫ 0 d ρ x dx wherein d = sample thickness and ρ = charge density, and wherein further - all samples have a thickness of 1 mm, - no silicone oil or grease is used at the interfaces of the samples, - for each parameter combination, a fresh and depolarized liquid silicone rubber sample is used, - the acoustic impulse is generated directly at the place of the space charge which allows to determine their position via the speed of the acoustic waves.
  13. Cured silicone compositions according to any of claims 11 to 12, having a volume resistivity in the range of 25 to 90 °C at an electric field of 10 kV/mm to 30 kV/mm of preferably greater than 1*10 11 Ohm*cm, more preferably greater than 1*10 13 Ohm*cm, more preferably greater than 1*10 16 Ohm*cm, and even more preferred greater than 1*10 17 Ohm*cm, preferably up to 1*10 18 Ohm*cm, and/or having a volume resistivity in the range of 25 to 90 °C at an electric field of 10 kV/mm to 30 kV/mm of between 1*10 11 and 1*10 19 Ohm*cm, preferably between 1*10 11 and 1*10 18 Ohm*cm, preferably between 1*10 13 and 1*10 18 Ohm*cm, more preferably between 1*10 14 and 1*10 18 Ohm*cm, and most preferably between 1*10 16 and 1*10 18 Ohm*cm.
  14. An insulator or a field grading assembly for high voltage direct current application which is obtained by curing the curable silicone composition according to any of the previous claims.
  15. Curable composition comprising the non-curable silicone composition according to any of the previous claims, comprising: a) 100 pt.wt. of one or more polyorganosiloxanes a2) having one or more unsaturated groups, preferably one or more alkenyl groups, b) 0 - 100 pt.wt. of a crosslinker component comprising one or more polyorganohydrogensiloxanes, c) 0 - 100 pt.wt. of one or more filler components, comprising one or more reinforcing silicas or resins, d) more than 2 pt.wt., preferably 4 pt.wt. - 12 pt.wt. of one or more carbon blacks, e) a curing catalyst selected from the group consisting of a compound enabling hydrosilylation and an organic peroxide, and f) 0 - 50 pt.wt. of one or more auxiliary additives. and cured silicone compositions obtained by curing said curable silicone compositions.

Description

The present invention relates to a process for the manufacture of a non-curable silicone composition comprising carbon black, the non-curable silicone composition obtained by the process and its use for the manufacture of curable silicone compositions in particular for use in high voltage direct current applications. Standard silicones are widely used in high voltage (HV) industry for alternating current (AC). However, the use of those materials fails in the emerging trend for direct current (DC) application. The use of carbon black (CB) as filler material provides an advantageous property to the silicone with positive tests up to 325 kV working voltage with a standard CB paste which is established for many years. This standard CB paste is produced via three roll mill technology or a twin blade kneader (US20170372815A1). The present inventors found out, however, that there are limitations at higher voltages of up to 500 kV, by causing breakdowns of the modified silicone system. Also, the current conductive liquid silicone rubbers (LSR) are very limited in variation of mechanical properties and have in some cases insufficient electrical conductivity. Silicone compositions comprising carbon black as filler are for example disclosed in the following documents of the state of the art: WO2016/110570 and US20170372815A1, respectively, disclose the use of a silicone composition comprising a) at least one polyorganopolysiloxane having alkenyl groups,b) a crosslinker component comprising one or more polyorganohydrogensiloxanes,c) a filler component comprising one or more reinforcing silicas or resins,d) at least one dielectric active compound, ande) a curing catalyst,wherein the dielectric active compound d) may be selected from carbon black, i.e. they disclose the use of a curable silicone composition, while the present application is directed at the use of a non-curable silicone composition. Further, WO2016/110570 discloses a method for the manufacture of an insulator or a field grading assembly comprising the shaping of the above-cited silicone composition by extrusion through a nozzle or a mould, and then curing the shaped composition by heat or light. While the present application relates to a process comprising the extrusion of a non-curable silicone composition comprising carbon black, and to a curable silicone composition comprising such specific non-curable carbon black silicone composition obtained by a process comprising an extrusion step, resulting in improved properties of the cured silicone compositions for DC applications based on such carbon black paste, WO2016/110570 and US20170372815A1 disclose extrusion as a means of shaping of a curable silicone composition as defined above. US2004/138370A1 discloses a silicone composition for the use as a conductive liquid rubber composition in e.g. printers, comprising a) polyorganopolysiloxane having alkenyl groups,b) at least one dielectric active compound, namely carbon black,c) a curing catalyst,d) a cross-linker comprising an organopolysiloxane having two or more silicon-bonded hydrogen atoms in one molecule, wherein the above-cited components are preferably supplied continuously to a mixing apparatus. The mixing apparatus may be, among others, an extruder. Accordingly, while in the present application extrusion is a mandatory step in the provision of a non-curable carbon black silicone paste, US2004/138370A1 discloses that the mixing step of all components constituting a curable silicone composition as described therein may be effected by an extruder. WO2020/063799A1 relates to a conductive liquid silicone rubber composition comprising carbon black, comprising a) one or more polydiorganosiloxane(s) having at least two alkenyl groups per molecule,b) at least one organohydrogenpolysiloxane,c) at least one reinforcing filler,d) at least one hydrosilylation catalyst, ande) an electrically conductive filler containing (i) extra conductive carbon black, and(ii) single walled carbon nanotubes, i.e. it relates to a curable silicone rubber composition. With respect to such curable silicone rubber composition, extrusion is mentioned as means for processing or forming the above-cited curable silicone rubber composition, and thus serves a different purpose than in the present application, which relates to the manufacture of a non-curable carbon black silicone masterbatch using an extrusion process. WO2009/027133A2 relates to a process for the manufacture of shaped cured silicone articles comprising a shaping step that comprises the continuous shaping of a curable silicone mixture. According to the disclosure of this document, a part of said mixture, i.e. the part of the uncured mixture of the components (i) at least one linear polyorganosiloxane having at least three alkenyl groups and an average number of diorganosiloxy units determined by GPC with polystyrene as standard of at least 3000,(ii) optionally one or more polyorganosiloxane having alkenyl groups, other th