Halogen-free mixture, a self-extinguishing prepreg containing th

Details Halogen-free mixture, a self-extinguishing prepreg containing th Halogen-free mixture, a self-extinguishing prepreg containing th

1995-06-19

1997-07-15

Clark, W. Robinson H.

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

525482, 525485, 525506, 525507, 524404, 524405, C08L 6304, C08L 6106

Patent

active

056484364

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The invention relates to a halogen-free resin mixture comprising an epoxy resin, a hardener, a flame retardant as well as additives, a self-extinguishing prepreg consisting of this resin mixture as well as its advantageous application, particularly as an insulation material.


STATE OF THE ART

European Patent EP-A-365784 teaches the preparation of resin mixtures consisting of an epoxy resin with flame retardants in order to make fire-resistant semi-finished products (prepregs). As flame retardants, halogen-free phosphorus and nitrogen compounds are suggested. These flame retardants however have the disadvantage, that in the instance of fire they disintegrate releasing corrosive and partly toxic compounds like nitrogen oxide and derivatives of phosphoric acid, which during the use of the preparation cause corrosion damage of machine parts.
The use of flame retardants like magnesium hydroxide and zinc carbonate is also possible, because it is known that they do not form any corrosive products on disintegration in the instance of fire. However, semi-finished products (prepregs) consisting of a resin of the type mentioned hereinabove under use of the flame retardants do not fulfil either the high requirements with respect to resistance against fire nor can they be formed into laminates with permanent temperature resistance during hardening (greater or equal to thermal class F).
Further, prepregs of the type mentioned above have to fulfil high requirements with respect to their application. An important criterion for their use are their adhesive properties. Especially in mechanical engineering such type of semi-finished products (prepregs) constitute important connecting elements between individual machine parts as well as between the used material, whereby a rigid stable connection between the individual machine parts or materials is to be achieved.
Therefore an object of the invention is to provide a halogen-free resin mixture of the type mentioned hereinabove, which provides prepregs that do not exhibit known disadvantages like the release of corrosive or toxic compounds in the instance of fire and at the same time have a high fire resistance and permanent temperature resistance as well as good adhesive properties. For the solution of this problem, according to the invention there is provided a halogen-free resin mixture composed of: an epoxidised phenol novolak or kresol novolak.
Further the invention relates to a self extinguishing prepreg with a resin mixture content of 40-200% produceable by application of a halogen-free resin mixture composed of:
Advantageously, the self extinguishing prepreg has a resin mixture content of 40 to 140 percent.
Preferably, glass fibers, aramide fibers and acryl fibers are used as carrier materials. These are advantageously used in the form of a web of fibers, a fabric or a fleece.
Further the carrier material may be in the form of a plastic foil. Especially good properties of prepregs are reached when the epoxy resin is one of the type of an epoxidised phenol novolak or kresol novolak.
Advantageously the prepreg according to the invention is used as an insulation material in electrical machines and converters.


A METHOD FOR EXECUTION OF THE INVENTION

An impregnating resin mixture according to the invention has the following constituents:


______________________________________ Main Components Quantity ______________________________________ Epoxy novolak/solid resin content 75% 118 g Phenolic novolak hardener/solid resin content 65% 203 g zinc borate 100 g ______________________________________
As additives, an amorphous silicon dioxide (trademark name Aerosil) to an extent of 2 g and an accelerator, e.g. benzyldimethyl amine in a quantity of 0.2 g are added.
The above mentioned ingredients are introduced in the form of an acetonic suspension on a glass filament fabric (200 g/m square) and are dried in a vertical dryer at temperatures up to 170.degree. C. (prepreg A).
Instead of the above used zinc borate, now in the same quantity the fo

REFERENCES:
patent: 2785144 (1957-03-01), Wachter
patent: 5019605 (1991-05-01), Jannic
patent: 5059637 (1991-10-01), Langer
Chemical Abstracts, vol. 106, No. 2, 1 Jun. 1987, Columbus, Ohio, US; Abstract No. 177805, "Epoxy Resin Potting Compositions".

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