Duroplastic-bonded molded fiber parts and method for producing the same

#The invention relates to thermoset-bound fiber moldings produced from fiber material based on natural and/or synthetic fibers and bound by means of a thermoset binder.

#Moldings produced from fibers are used, for example, as climate-regulating sound-absorbing articles and shaped articles possessing high surface strength and splintering resistance in automobile vehicle construction for example. Such moldings are typically produced from nonwoven fibrous layers bound with phenolic resin by press molding with concurrent curing.

#These products have the disadvantage that they occasionally, in particular after exposure to elevated temperatures and moisture, give off a noticeable odor which is mostly due to the curing agent (hexamethylenetetramine) and/or its aminic decomposition products.

#The binder Bakelite® PF 7077 TP (product of Bakelite AG, Germany) was admixed with the stated amounts of activated carbon (based on the binder), this mixture was applied to the fiber material and distributed in the fiber web, and this was followed by pressing at 190° C. for 5 min to cure the binder. The component was then heated at 80° C. or 100° C. for 5 h and analyzed by gas chromatography. The reported values are averages of the area below the curve from 3 measurements:

#Mean area of fast Mean area of Mean area of Mean total area volatiles slow volatiles phenol Measurement Measurement Measurement Measurement at 5 h at 5 h at 5 h at 5 h Constituent 80° C. 100° C. 80° C. 100° C. 80° C. 100° C. 80° C. 100° C. Pure Bakelite ® 11354 25030 809 2119 10545 22911 8094 15013 PF 7077 TP binder: phenol novolac with hexamethylenetetramine and reaction accelerant Pure fibre: 9398 45457 7517 40886 1881 4571 31 504 pulled cotton with 15%-30% synthetic fibre Pure activated carbon: 208 1167 208 1049 0 91 0 0 ABP 850 (from Adaks-Pica GmbH, Germany) pulverulent Binder with 5% of activated 3038 12720 716 9038 2322 3682 2395 492 carbon Binder with 10% of activated 314 9022 314 6570 0 2477 0 0 carbon Binder with 15% of activated 328 6496 328 4829 0 1666 0 0 carbon

#The table reveals that the addition of just 5% of activated carbon is sufficient to distinctly reduce the emission of phenols at least. These results suggest that thermoset fiber moldings produced by conventional processes will no longer release odorants in use even under extreme conditions (hot, humid air). Losses in relation to other properties such as mechanical, sound-absorbing and fire properties were not observed.