METHOD FOR PREPARING PENTAERYTHRITOL WITH CONTENT OF BASIC SUBSTANCE ABOVE 98 MASS % AND PENTAERYTHRITOL ENRICHED WITH DIPENTAERYTHRITOL IN AMOUNT 5-20 MASS % Russian patent published in 2003 - IPC

FIELD: chemical technology. SUBSTANCE: invention relates to the improved method for preparing pentaerythritol with the content of basic substance above 98 wt. -% and pentaerythritol enriched with dipentaerythritol in the amount 5-20 wt.-% used in paint and varnish and other branches of industry. Method involves condensation of acetaldehyde with formaldehyde in an aqueous alkaline medium, the following neutralizations of reaction mixture, desorption of formaldehyde excess, evaporation, crystallization under vacuum at 45-55 C and density of suspension ρ₅₀ = 1.30-1.35 g/cm³, filtration, washing out the prepared technical pentaerythritol, its the following recrystallization in hot water at 45-55 C and drying resulting to isolation of pentaerythritol with content of basic substance above 98 wt.-%. Then technical pentaerythritol suspension filtrate and filtrate from the stage of recrystallization are combined, evaporated, subjected for crystallization under vacuum at 38-45 C, formed suspension if filtered off, precipitate is washed out, recrystallized again in hot water, precipitate is filtered at 45-55 C and dried to yield pentaerythritol enriched with dipentaerythritol in the amount 5-20 wt.-%. As a rule, the precipitate obtained after stage of crystallization under vacuum at 38-45 C and filtration is carried out with demineralized water and/or filtrate enriched with pentaerythritol taken from the recrystallization stage. Usually, at stages for preparing pentaerythritol with the content of basic substance above 98 wt.-% the latter is isolated in the amount 55-74 wt.-%. Method ensures to improve quality the prepared pentaerythritol, to obtain valuable product additionally, to enhance the total degree of isolation of pentaerythritol and to reduce consumption norms by the main raw species. EFFECT: improved preparing method. 3 cl