Lightweight shaped articles containing expandable graphite, their production and their use

#The present invention relates to sandwich-like lightweight shaped articles, the core material of which contains expanded expandable graphite, and a process for their production and their use.

#Known sandwich-like lightweight shaped articles having a relatively high heat resistance contain as the core material, for example, foamed glass which has been joined to the covering layers by glueing. The disadvantage of these is that the heat resistance is not high enough for many purposes, and the production of specifically shaped lightweight articles is difficult.

#Sandwich-like lightweight shaped articles have now been found, which are characterised in that their core material contains expandable graphite expanded according to the mould, and at least one covering layer consists of a thermoplastic material.

#In the following examples, parts and percentages relate to the weight, unless stated otherwise.

#Commercially available NO.sub.x expandable graphite which expands to more than 15 times its volume when heated to 600.degree. C. under normal pressure was mixed with a binder which was prepared by reaction of 1 mol of aluminium hydroxide, 3 mol of dimethyl methylphosphonate and water in an autoclave at 180.degree. C. and was obtained as a clear aqueous solution.

#A steel mould consisting of a spacer frame of low-scaling steel which had internal dimensions of 12.times.12.times.2.5 cm, lay on a steel sheet and was covered with a steel sheet, the spacer frame and the steel sheets being made of material 8 mm thick, was pressed together by screwing. The mould was talced and assembled horizontally, apart from the steel covering sheet. A 2 mm thick flat sheet of commercially available polyphenylene sulphide was laid in the spacer frame, this sheet was then coated uniformly with 40 g of the mixture consisting of expandable graphite and binder, and finally a second, corresponding sheet of polyphenylene sulphide was placed on top.