Abstract: The present invention relates to hard foams having foamed and hardened phenolic resins as binding agents, and in which over 90% of the filler is aluminum hudroxide. The filler content is more than 100% with respect to the resin content of the foams. The foamble, filler-containing composition used for the production of the foams is very fluid and can be used directly for the production of moldings of any desired geometry. The aluminum hydroxide used has a grain size distribution such that between 30 to 60% of the filler is in the grain size range under 5 microns. The moldings containing the hard foam can also be in the form of composites. They are characterized not only by their good insulating properties but also by improved compressive strength, extremely little shirinkage tendency and extraordinarily high fire resistance. They are used mainly in the construction industry.

Abstract: The present invention relates to foams made of resol-type phenolic resins which do not discolor as quickly as prior-art phenolic foams. With the additive in accordance with the invention, even colored foams will not darken as readily. The foams in accordance with the invention contain as stabilizers salts of phosphinic acid or phosphonic acid, such as the primary alkali phosphites or the alkali phosphinates. The stabilizers, which protect the foams against the action of light and/or air and/or heat, are used in amounts ranging from 0.1 to 5 weight percent. The present invention further relates to methods of preparing such foams. In a preferred method, the stabilizers are admixed with an expandable resol-type phenolic resin, the mixture so obtained is mixed with the other substances necessary to formation of a foam, and the whole mixture is then foamed conventionally.