Composite insulating materials with good flexural-tensile strength - by foaming suspension of alkali water glass, mineral filler and blowing agent round core of known (in)organic insulating material

Composite prods. made of insulating material, with good flexural-tensile resistance and mean bulk density 40-90 kg/m3 are claimed (I). (I) are produced from a known inorganic or organic insulating material (II) by covering it with foam made from a suspension of alkali water glass (IIIA), mineral fillers (IIIB) and blowing agent (IIIC). In producing (I) as above, in which the foam is produced by heating the suspension (III) to 70-90 deg.C. (II) is a plastic foam which is impregnated all round with an unfoamed suspension of (IIIA) and (IIIB), or a glass or mineral fibre mat, pref. a foamed mixt. of (IIIA) and (IIIB). The surface of (I) is impregnated with an unfoamed suspension of (IIIA) and (IIIB) on at least one side (pref. all sides), and/or the outer layers of (I) are reinforced with high-tensile material (IV) on at least one side (pref. all sides). (IV) is metal foil, e.g., Al foil, or woven wire fabric. The suspension for foaming (III-F) contains 40-60 wt.% aq. soln. (IIIA), 32-48 wt.% (IIIB) and 6-12 wt.% (IIIC), pref. azodicarbonamide (AXDC), and the suspension for impregnating (III-IMP) contains 90-10 wt.% soln. (IIIA) and 10-90 wt.% (IIIB), pref. Al2O3, SiO2, ZrO2, TiO2, graphite, red mud, quartz powder, aluminous cement and/or kaolin, with particle size 1-30 microns; pref. (IIIA) has density 35-40 deg. Beaume. USE/ADVANTAGE - Provides relatively low density insulating materials (boards, sheeting, tubes, etc.), with good thermal conductivity (0.03-0.04 W/mK), temp. resistance up to at least 1200 deg.C, and high resistance to fracture and flexural-tensile loading. (I) are environmentally acceptable (recyclable raw materials, no emissions of fibres or toxic substances, no toxic fumes in case of fire).