Core mixture based on modified lignosulfonate.

Abstract

Technical lignosulfonates (LST) are a by-product in the production of cellulose by the sulfite method. Lignosulphonates are the third most widely used binder in foundries (after clay and liquid glass). They are used for rawforming, dryforming, making rods in heated tooling, non-stick paints, etc. Molding mixtures with only one LST are not used, as they have low strength due to the occurrence of stresses and cracks in the films of this binder. In addition, LST, like all water-soluble binders, have a suspended hygroscopicity, which reduces thestrength of the rod (mold) during storage. However, when hydrophobic additives are introduced into the LST, the latter disadvantage decreas-es.Previously, calcium hydrosulfate (cooking acid with a calcium base) was used for sulfite cooking of cellulose and calcium lignosulfanates were in the LST. Now mainly cooking acids with sodium mixed with Ca–Na are used, and an-yway, the strength properties for mixtures are insufficient. In order to eliminate these disadvantages, plasticisers and modifiers are added to LST. For forming raw, dry and making rods, LST with a sodium base is used, lignosulfonate modified with hexavalent chromium (CrO3) is used, clay mixtures are introduced, LST is used with other binders, as a combined binder (for example, USK). The aim of the work is to develop a modifying additive based on the binder LST-USK, a component of the core mixture used at JSC “NTKRZ”, which is not inferior to the known core compositions, with its subsequent possible use in production. As a second additive, and the possibility of introducing it in production, the composition of the core mixture with sunflower oil was tested on the casting radiator MS-140-M2-500.