Glimmerband zur Herstellung einer mit einer heisshärtenden Epoxydtränkharzmischung imprägnierten Isolierhülse für elektrische Leiter

1,011,417. Insulation for dynamo-electric machines. SIEMENS - SCHUCKERTWERKE A.G. June 25, 1962 [June 23, 1961], No. 24407/62. Drawings to Specification. Heading H2A. [Also in Division B5] Sheet or tape insulation for the conductor bars of electrical machines comprises inorganic lamellµ, e.g. mica flakes, bonded to a flexible backing, e.g. paper, fabric or plastic foil, by non-self-hardening but hardenable bonding agent, the sheet or tape containing an accelerator which will promote the polyaddition reaction of a thermosetting epoxide resinhardener mixture (with which the wound-on insulation is subsequently to be impregnated) but which does not promote the ionic homopolymerization of the bonding agent. Preferably the accelerator is contained in the bonding agent, the total amount of accelerator present being between 0.1 and 0À4% of the total weight of the sheet or tape, the bonding agent having viscosity between 25 and 10,000 poises at 25‹ C., examples being given, whilst the accelerator may be e.g. (i) a mixed aliphatic-aromatic amine in which the amino nitrogen atom is directly linked to the aromatic portion of the amine, (ii) a zinc salt which is soluble in organic solvents, or (iii) a complex boron compound in which the election octet gap of the boron atom is filled by a free election pair of a nitrogen atom of an amine, examples of each of the above being given. The hardener with which the insulation is impregnated after it has been wrapped on to the conductor bar is a thermosetting expoxide resin mixture based upon bi- or polyfunctional glycidyl ethers or epoxide compounds and acid anhydrides and impregnation is effected at about 60‹ to 70‹ C. to ensure that the viscosity of the mixture is below 30 cP. Several layers of mica flakes may be formed on a backing sheet and a further backing sheet laid on top.