Patent GB-801404-A (GB)
Title: A new or improved method for production of stable solid water-soluble aminoplastic condensation products
IPC: C08G12/02
Filed: 1956-02-13
Abstract: Stable solid water-soluble condensation products between (i) amido-derivatives of carbonic acid apt to form aminoplasts with formaldehyde and (ii) formaldehyde or formaldehyde forming compounds are formed by preparing an aqueous solution of such a condensation product, heating it for not more than 60 seconds to a temperature exceeding the melting point of the resultant substantially anhydrous product, withdrawing it from the heating zone in molten condition, and cooling it so as to cause it to solidify.  The preparation may be two-stage or continuous, higher reaction temperatures being used in the continuous process (e.g. higher than 70 DEG  C.) and the relative duration of reaction and dehydration being adjusted as appropriate. A falling film evaporator whose steam jacket temperature is kept at 110-180 DEG  C. is the preferred method of evaporation: the heating may last for less than 15 seconds in the case of quick-polymerizing condensates.  The cooling may be by cooling drum, by granulating tower or by casting.  Urea, thiourea, guanidine and melamine are mentioned.  In Examples (1) and (2) dimethylolurea is formed by reacting formalin and urea at an alkaline pH and then passing it through a falling film evaporator.  In (3) monomethylolurea is formed by violent cooling of a reaction mixture of formaline and urea; the product was then passed through a steam jacketed pipe and an insulated pipe coil into the falling film evaporator to produce dimethylolurea as before.  In (4) melamine and formalin were reacted as in (1) with varying pressures, temperatures and rates of flow in the falling film evaporator for comparison; the preferred product was trimethylolmelamine.  In (5) a continuous apparatus is described consisting of (i) a liquid formaldehyde feeder with pump, motor and heating coil; (ii) a hopper for the amido-derivatives with screw conveyer; (iii) a mixer with float and stirrer; (iv) reaction coil with valve; (v) falling film evaporator; (vi) cooling drum.  Melamine and formalin were reacted as in (4), the dehydration being conducted at reduced temperature and pressure to produce trimethylolmelamine. In (6) urea and formalin were reacted in the continuous apparatus of (5) but at normal pressure.  Specification 601,983 is referred to.ALSO:Stable solid water-soluble condensation products between (1) amido-derivatives of carbonic acid apt to form aminoplastic resins with formaldehyde and (ii) formaldehyde or foraldehyde-forming compounds are formed by preparing an aqueous solution of such a condensation product, heating it for not more than 60 seconds to a temperature exceeding the melting point of the resultant substantially anhydrous product, withdrawing it from the heating zone in molten condition and cooling it so as to cause it to solidify. The preparation may be two-stage or continuous, higher reaction temperatures (e.g. higher then 70 DEG  C.) being used in the continuous process, and the relative duration of reaction and dehydration being adjusted as appropriate.  A falling film evaporator whose steam jacket temperature is kept at 110-180 DEG  C. is the preferred method of evaporation; the heating may last for less than 15 seconds in the case of quick-polymerizing condensates.  The cooling may be by cooling drum, granulating tower or casting.  Urea, thiourea, guanidine and melamine are mentioned as suitable carbamic acid amido derivatives.  In examples: (1) and (2) dimethylolurea is formed by reacting formalin and urea at an alkaline pH and then passing it through a falling film evaporator.  In (3) monomethylurea is formed by violent cooling of a reaction mixture of formalin and urea; the product was then passed through a steam jacket pipe and an insulated pipe coil into the falling film evaporator to produce dimethylolurea as before.  In (4) melamine and formalin were reacted as in (1) with varying pressures, temperatures and rates of flow into the falling film evaporator for comparison; the preferred product was dimethylol melamine.  In (5) a continuous appratus is described consisting of (i) a liquid formaldehyde feeder in the pump, motor and heating coil; (ii) a hopper for the amido derivatives with screw conveyer; (iii) a mixer with float and stirrer; (iv) reaction coil in the valve; (v) falling film evaporator; (vi) cooling drum: melamine and formalin were reacted as in (4), the dehydration being conducted at reduced temperature and pressure to produce dimethylol melamine. In (6) urea and formalin were reacted in the continuous apparatus of (5) but at normal pressure.  Specification 601,983 is referred to.