Melamine resin prepregs and laminates with improved mechanical properties - contain fibre reinforcement impregnated with etherated MF resin modified with mixts. of diol(s)

摘要

Melamine-formaldehyde (MF) resin prepregs or laminates (I) comprise strips of fibre reinforcement (II) impregnated with etherated, modified melamine resin (III) consisting of (a) 40-85 wt.% at least partly etherated MF resins obtd. by reaction of melamine, formaldehyde and 1-8C alkanols in the mol. ratio 1:(5-6):(4-6) and (b) 60-15 wt.% diols contg. 25-75 wt.% polyester- and/or polyether-diols with mw. at least 400 (b1) and 75-25 wt.% low mw. 2-12C diols (b2). Prodn. of (I) comprises impregnation of (II) with (III) as above, opt. followed by partial or complete hardening of the prepreg obtd. Specifically (III) contains 50-70 wt.% (a) (pref. modified with 1-4C alkanols) and 50-30 wt.% (b) comprising 40-60 wt.% (b1) (esp. condensation prods. of adipic and/or phthalic acid with ethylene glycol and/or 1,4-butanediol, and/or poly-THF-diols) and 60-40 wt.% (b2). (II) is (non)woven fabric or mat based on glass, carbon or aramid fibre. USE/ADVANTAGE - W.r.t. prior-art MF resin prepregs and laminates, (I) have improved mechanical properties (esp. higher impact strength) and lower shrinkage on curin