Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Patent
1995-10-27
1998-05-26
Krass, Frederick
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
528 99, 528398, 525523, 428413, C08G 5940
Patent
active
057566380
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to novel phosphorus-containing epoxy resins, a process for the preparation thereof and the use thereof. The novel phosphorus-containing epoxy resins, besides being flame-resistant, are, in particular, very easy to process since they have, inter alia, good storage stability.
Epoxy resins are nowadays used on a large scale for the preparation of moldings and coatings having a high level of thermal, mechanical and electrical properties and also for the production of laminates. The low molecular weight or oligomeric starting components can be reacted to form high-grade thermosetting materials using a great variety of hardeners such as, for example, carboxylic anhydrides, amines, phenols or isocyanates. A further advantage of epoxy resins is their processing behavior. In the initial state they are low molecular weight or oligomeric and have a low viscosity at processing temperatures. They are therefore very suitable for encapsulating complex electrical or electronic components and also for impregnation processes. In the presence of suitable reaction accelerators they have satisfactory pot lives. They are also highly fillable with conventional inert inorganic fillers.
In order that in the event of a fire or accident people may be protected and the continued functioning of electrical or electronic devices may be ensured for a certain time, flame resistance is nowadays frequently required cured of epoxy resin materials in electrical engineering. This means that the cured epoxy resin moldings have to be self-extinguishing and must not spread the fire. The detailed requirements are prescribed in the standards applicable to the respective product. Cured epoxy resins used in electronics or electrical engineering must chiefly satisfy the flammability test requirements of UL 94V.
A summary of the possible methods for making epoxy resins flame-resistant can be found in the literature (e.g. Troitzsch, J., "International Plastics Flammability Handbook", 2nd edition, Carl Hanser Verlag, Munich, 1990; Yehaskel, A., "Fire and Flame Retardant Polymers, Noyes Data Corporation, New Jersey, USA, 1979).
Epoxy resins are nowadays generally made flame-resistant by means of halogen-containing, specifically bromine-containing, aromatic components. The resins in question usually contain a filler or glass fabric and frequently also antimony trioxide as a synergist. The problem with this is that in the event of an accident carbonization or combustion can form corrosive and, under unfavorable conditions, ecologically or toxicologically unsafe decomposition products. Considerable technical effort has to be expended for safe disposal by incineration.
There is therefore a considerable need for epoxy resins which achieve the combustion resistance required in the standards without the addition of halogenated components.
An effective way of achieving flame resistance in resin-type substrates has been found to be the use of organic phosphorus compounds. Attempts have therefore already been made to modify epoxy resins with additives based on phosphoric esters such as, for example, triphenylphosphate (DE 1 287 312). However, these compounds migrate out of the cured materials to the surface, particularly at elevated temperature, where they affect the dielectric properties and lead to electro-corrosion.
Epoxy resins having chemically bound phosphorus could be obtained by reacting commercial epoxy resins with the P-OH groups of various phosphoric acids, the P-OH group being added to the oxirane ring and simultaneously causing partial epoxy polymerization. This gives phosphorus-modified epoxy resins which are still reactive and which are bound into the network on curing.
Examples of the crosslinking of epoxy resins with phosphoric acid, acid phosphoric esters and pyrophosphate diesters as acidic crosslinking agent are described in U.S. Pat. No. 2,541,027. Here, in part, corresponding reaction products are first prepared, these being subsequently crosslinked. These reaction products are not storage-stable. Similar products
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Huber Jurgen
Kapitza Heinrich
Kleiner Hans-Jerg
Rogler Wolfgang
Schonamsgruber Uwe
Hoechst AG
Krass Frederick
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