Method for the production of insulation plates and binding agent mixture for same

#The invention relates to a method for the production of refractory insulation plates comprised of mineral fillers, cellulose-containing products and a thermosetting binding agent.

#Such plates are employed, inter alia, as mold covering plates or as so-called tundish plates in continuous casting processes. They are produced by heating and curing a mixture preformed into the corresponding plate form, which is produced by removing water from an aqueous pulp comprised of cellulose-containing products, mineral fillers and a thermosetting binding agent. For this purpose, the pulp is poured onto a fine screen and the water is extracted under vacuum, but this process step is highly time-consuming and a need exists to shorten it.

#The conventionally employed thermosetting binding agent is a mixture of a novolak and a curing agent, wherein a relatively highly condensed product must be used having an average molecular weight of 800 to 900 and a flow distance of approximately 20 to 30 mm as the novolak. With these novolaks, however, only moderate strengths of the insulation plates are attained. An improvement of the strength values results if novolaks with lower average molecular weights or greater flow distances are used. However, these binding agents swell more strongly in the pulp and thereby, the water extraction times are drastically increased, so that the use of these resins is not suitable for reasons of economy.

#The novel resin mixture of the invention is derived by pulverizing a solidified melt of a novolak and as an additive, at least one member selected from the group consisting of fatty acid amides and substituted fatty acid amides.

#The improved method of the invention to produce insulation plates comprises forming a resin powder of a solidified melt of a novolak and at least one additive selected from the group consisting of fatty acid amides and substituted fatty amides, forming an aqueous pulp of said resin powder, cellulose containing products and mineral fillers, pouring the aqueous pulp onto a fine-mesh flat screen and extracting the water under vacuum to obtain a “green” filter cake plate and curing the plate at a temperature of at least 120° C., preferably 150° C.

#By employing an aqueous pulp comprised of cellulose-containing products, mineral fillers and novolak, which additionally contain at least one product selected from the group consisting of fatty acid amides or substituted fatty acid amides, the water extraction times are significantly shortened. The strength of the plates produced from these mixtures is not impaired by this addition. It was further found that these additives from the group of fatty acid amides or substituted fatty acid amides make it possible to use novolaks with lower average molecular weight, i.e. with greater flow distance, without the water extraction time being lengthened. Therefore, insulation plates are obtained whose strengths are 30% higher than those produced by prior art methods.