GB601983A - Manufacture of aminotriazine-aldehyde reaction products - Google Patents

Abstract

Solid aminotriazine-aldehyde condensation products, soluble in all proportions in water at ordinary temperature, are formed by reacting an aqueous mixture of an aminotriazine and a water-soluble aldehyde to form a clear solution capable of unlimited dilution with water without precipitation, dehydrating the solution so rapidly that the dry product has unlimited solubility in water and immediately cooling the dry product to 80 DEG C. or lower. Preferably the solution is spray dried but it may be dried on a drum preferably in vacuo. The reaction mixture is preferably kept alkaline. Suitable aminotriazines are melamine, ammeline, ammelide, 2, 4, 6,triethyl- or triphenyl-triamino-1, 3, 5-triazine; 2, 4, 6-trihydrazino-1, 3, 5-triazine; melam; melem; 2-amino-1, 3, 5-triazine; 2-chloro-4,6-diamino-1,3,5-triazine; 2 - phenyl - 4 - amino - 6 - hydroxy-1,3,5-triazine; and 6-methyl-2,4-diamino-1,3,5-triazine or mixtures thereof. Suitable aldehydes are formaldehyde, acetaldehyde, propionaldehyde, glycollic aldehyde, glyoxylic aldehyde, crotonaldehyde, acrolein, tiglic aldehyde, chloral, or glyoxal. The clear solution is preferably kept above crystallisation temperature before drying or it may be diluted to prevent crystallisation. Four examples describe the preparation of melamine formaldehyde condensation products with varying initial proportions of the reactants and of water. Example 5 describes the preparation of a condensation product from ammeline and formaldehyde. A continuous method of operation is described which avoids the difficulty when drying large patches of material that the last portions stand longer before drying than the first ones. In the method described predetermined quantities of reactants are fed to a reaction kettle, the pH of the mixture is adjusted and the reaction allowed to proceed. The clear solution is then filtered without being allowed to crystallise, stored and then continuously passed to a spray drier, the dried product cooled below 80 DEG C. passed to a powder recovery process and continuously removed and packed. At an appropriate time after starting a reaction in one kettle, a reaction is started in a second kettle so that a continuous supply of clear solution is available for drying. In a modification the reaction mixture may flow continuously through a reactor the temperature and length of which are related to produce a product which can pass immediately to the dryer. Aqueous solutions of the products are suitable for coating or impregnating, as adhesives or as intermediates for preparing etherified resins. Acidic or basic hardening agents may be added to the products. Plasticizers, colouring matters or other resins may also be added. Mixtures with hydroxylated vinyl resins containing sufficient OH groups to be self-dispersible in water are particularly useful. Specification 574,016 is referred to.ALSO:Solid aminotriazine-aldehyde condensation products, soluble in all proportions in water at ordinary temperature are formed by reacting an aqueous mixture of an aminotriazine and a water-soluble aldehyde to form a clear solution capable of unlimited dilution with water without precipitation, dehydrating the solution so rapidly that the dry product has unlimited solubility in water and immediately cooling the dry product to 80 DEG C. or lower. Preferably, the solution is spray dried, but it may be dried in a drum, preferably in vacuo. The reaction mixture is preferably kept alkaline. Suitable aminotriazines are melamine, ammeline, ammelide, 2,4,6-triethyl- or triphenyl-triamino-1,3,5-triazine; 2,4,6-trihydrazine-1,3,5-triazine; melam; melem; 2-amino-1,3,5-triazine; 2-chloro-4,6-diamino-1,3,5-triazine; 2-phenyl-4-amino-6-hydroxy-1,3,5-triazine; and 6-methyl-2,4-diamino-1,3,5-triazine or mixtures thereof. Suitable aldehydes are formaldehyde, acetaldehyde, propionaldehyde, glycollic aldehyde, glyoxylic aldehyde, crotonaldehyde, acrolein, lighter aldehyde, chloral or glyoxal. The clear solution is preferably kept above crystallization temperature before drying or it may be diluted to prevent crystallization. Four examples describe the preparation of melamino-formaldehyde condensation products with varying initial proportions of the reactants and of water. Example 5 describes the preparation of a condensation product from ammeline and formaldehyde. A continuous method of operation is described which avoids the difficulty when drying large batches of material that the last portions stand longer before drying than the first ones. In the method described, predetermined quantities of reactants are fed to a reaction kettle, the pH of the mixture is adjusted and the reaction allowed to proceed. The clear solution is then filtered without being allowed to crystallize, stored and then continuously passed to a spray drier, the dried product cooled below 80 DEG C. passed to a powder recovery process and continuously removed and packed. At an appropriate time after starting a reaction in one kettle, a reaction is started in a second kettle so that a continuous supply of clear solution is available for drying. In a modification, the reaction mixture may flow continuously through a reactor, the temperature and length of which are related to produce a product which can pass immediately to the dryer. Aqueous solutions of the products are suitable for coating or impregnating, as adhesives or as intermediates for preparing etherified resins. Acidic or basic hardening agents may be added to the products. Plasticisers, colouring matters or other resins may also be added. Mixtures with hydroxylated vinyl resins containing sufficient OH groups to be self-dispersible in water are particularly useful. Specification 574,016 is referred to.