Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant having at least one -n=c=x group as well as...
Patent
1981-10-07
1983-05-17
Cockeram, H. S.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant having at least one -n=c=x group as well as...
528 52, C08G 1830, C08G 1818, C08G 1816
Patent
active
043841015
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a resin mixture which is curable by thermosetting and is virtually free of volatile solvents, and which is suitable in particular as a highly heat-resistant impregnating, varnishing and casting resin for the insulation of electrical conductors and windings in electrical machinery and equipment, for example as an impregnating resin for electrical machinery of temperature rating H-C.
The mixtures known for this purpose, for example from German Auslegeschrift No. 2,444,458, consisting of epoxide compounds, polyisocyanates and a hardener based on morpholine compounds or imidazole compounds, have a pot life (measured time up to a doubling of the viscosity at 23.degree. C.) of only a few hours, which is generally far too short for economical production. To overcome the disadvantage of the excessively short pot life of such mixtures, it is known, for example from German Patent Specification No. 2,655,367, to use certain addition complexes of tertiary amines and boron trichloride as latent hardeners, instead of the morpholine compounds or imidazole compounds. This leads to a considerable increase in the pot life of the mixture, for example to more than 100 days, but at the same time leads to a deterioration in the mechanical properties of the mixture cured by thermosetting, to the extent that such mixtures are no longer directly suitable as insulating resins for high-utilization machinery, that is to say machinery which will withstand considerable heat in operation.
The object of the invention is to provide a resin mixture which is curable by thermosetting and is solvent-free (that is to say virtually free of volatile solvents), and which contains reactive liquid epoxide compounds and polyisocyanates as components, and also a latent hardener for these components, and has a pot life of the order of magnitude of a few weeks, without impairment of the mechanical properties.
This object is achieved according to the invention by using triallyl cyanurate as the crosslinking agent in such mixtures. Triallyl cyanurate (also abbreviated to TAC below) is a known and industrially obtainable compound of the formula ##STR1## in which R denotes the allyl radical, --CH.sub.2 CH.dbd.CH.sub.2. TAC is liquid above 28.degree. C. (melting point=27.3.degree. C.) and boils at 120.degree. C.; the ability of TAC to undergo addition reactions or copolymerization reactions, and its tendency to undergo extensive crosslinking, are in themselves to be expected from its structure containing three terminal olefin groups, and its use for improving the heat resistance of polyester resins is known.
However, it is surprising that, when added to the mixtures described above, TAC does not critically reduce their pot life, that is to say makes it possible to eliminate the disadvantages (short pot life) of the resin mixtures of German Auslegeschrift No. 2,444,458, without the disadvantages, hitherto associated therewith, of the resin mixtures according to German Auslegeschrift No. 2,655,367 (considerable deterioration in the mechanical properties of the cured mixture, that is to say of the thermosetting resin formed).
The components of resin mixtures according to the invention are illustrated below. Information on the thermosetting resin relates to the cured mixture.
In general, mostly relatively low-viscosity aliphatic, cycloaliphatic and aromatic, monomeric or oligomeric compounds, carbodiimides formed from the monomers, or mixtures thereof, are suitable here as polyisocyanates, in particular diisocyanates or triisocyanates. Aromatic polyisocyanates impart a relatively high heat resistance and good electrical properties (for example a high dielectric strength) to the thermosetting resin. Aliphatic polyisocyanates are preferably used for the most part only in comparatively small proportions, in order to plasticize the thermosetting resin. An isomer mixture of diphenylmethane 4,4'-diisocyanate and 2,4'-diisocyanate with a very low chlorine content, and/or isophorone diisocyanate, is preferred for many applications. The isomer m
REFERENCES:
patent: 3198851 (1965-08-01), Hoy
patent: 4022721 (1977-05-01), Ashida
patent: 4070416 (1978-01-01), Narahara et al.
patent: 4130546 (1978-12-01), Goto et al.
patent: 4143009 (1979-03-01), Dewey
patent: 4224422 (1980-09-01), Rude et al.
Kovacs Zoltan
Schuler Roland
BBC Brown Boveri & Company Limited
Cockeram H. S.
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