Improvements relating to the production of paraformaldehyde

摘要

Paraformaldehyde in a form which readily dissolves on heating with water is obtained by removing water from aqueous solutions of formaldehyde by distillation with organic liquids capable of producing with water azeotropic mixtures of low boiling point. The auxiliary liquid may, for example, be toluene, ethyl acetate, methyl ethyl ketone, diethyl formal, mesityl oxide, or ethylene dichloride; or the water may be removed in a ternary mixture by the simultaneous use of, for example, ethyl alcohol and diethyl formal. In the example, 1000 gms. of ethyl acetate are heated in a flask provided with a tall Raschig column. At a point two-thirds of the way up the column, a 40 per cent by volume solution of formaldehyde is run in at such a speed that the quantity of formaldehyde solution added agrees approximately with the quantity of water distilling off. The azeotropic mixture passing off at 70 DEG C. condenses to a mixture of 91,4 per cent of ethyl acetate and 8,6 per cent of weak formaldehyde solution. Paraformaldehyde separates in the flask, and by filtration and drying for a short time at 100 DEG C., may be freed from adhering solvent.ALSO:Paraformaldehyde in a form which readily dissolves on heating with water is obtained by removing water from aqueous solutions of formaldehyde by distillation with organic liquids capable of producing with water azeotropic mixtures of low boiling point. The auxiliary liquid may, for example, be toluene, ethyl acetate, methyl ethyl ketone, diethyl formal, mesityl oxide, or ethylene dichloride; or the water may be removed in a ternary mixture by the simultaneous use of, for example, ethyl alcohol and diethyl formal. In the example, 1000 gms. of ethyl acetate are heated in a flask provided with a tall Raschig column. At a point two-thirds of the way up the column, a 40 per cent by volume solution of formaldehyde is run in at such a speed that the quantity of formaldehyde solution added agrees approximately with the quantity of water distilling off. The azeotropic mixture passing off at 70 DEG C. condenses to a mixture of 91,4 per cent of ethyl acetate and 8,6 per cent of weak formaldehyde solution. Paraformaldehyde separates in the flask, and by filtration and drying for a short time at 100 DEG C., may be freed from adhering solvent.