1000-82-4Relevant articles and documents
Quantitative and qualitative 1H, 13C, and 15N NMR spectroscopic investigation of the urea-formaldehyde resin synthesis
Steinhof, Oliver,Kibrik, Eleonore J.,Scherr, Guenter,Hasse, Hans
, p. 138 - 162 (2014/04/03)
Urea-formaldehyde resins are bulk products of the chemical industry. Their synthesis involves a complex reaction network. The present work contributes to its elucidation by presenting results from detailed NMR spectroscopic studies with different methods. Besides1H NMR and13C NMR, 15N NMR spectroscopy is also applied.15N-enriched urea was used for the investigations. A detailed NMR signal assignment and a model of the reaction network of the hydroxymethylation step of the synthesis are presented. Because of its higher spectral dispersion and the fact that all key reactions directly involve the nitrogen centers,15N NMR provides a much larger amount of detail than do1H and13C NMR spectroscopy. Symmetric and asymmetric dimethylol urea can be clearly distinguished and separated from monomethylol urea, trimethylol urea, and methylene-bridged urea. The existence of hemiformals of methylol urea is confirmed. 1,3,5-Oxadiazinan-4-on (uron) and its derivatives were not found in the reaction mixtures investigated here but were prepared via alternative routes. The molar ratios of formaldehyde to urea were 1, 2, and 4, the pH values 7.5 and 8.5, and the reaction temperature 60 °C. Copyright 2014 John Wiley & Sons, Ltd. 15N-enriched urea is used in combination with quantitative15N and13C NMR spectroscopy and a Virtual Reference. This allows for a detailed peak assignment and absolute quantification of the early steps of this industrial process, which involves a complex reaction network. A detailed peak assignment for all three nuclei, a full quantitative description of the reaction mixture's composition and a model describing changes in shift depending on formaldehyde substitution are given. Copyright
Microbicidal mixtures
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, (2008/06/13)
The invention relates to synergistic mixtures of methyl-2H-isothiazol-3-one and 2-bromo-2-nitropropanediol for controlling microorganisms in industrial materials.
Binding of phenols in the urea-formaldehyde-water system and the role of precondensation stage in the synthesis of polymethyleneurea
Maslosh,Zamashchikov,Bezbozhnaya
, p. 1197 - 1200 (2007/10/03)
The precondensation stage (keeping of a solution of urea and formaldehyde in a neutral medium) in the synthesis of polymethyleneurea is examined experimentally and by mathematical simulation.
Process for producing methylol urea solution and process for producing slow-releasing nitrogenous fertilizer using the same
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, (2008/06/13)
A process for producing a methylol urea solution which comprises carrying out addition reaction between urea and formaldehyde in the presence of water and an alkali, wherein said alkali is a polyphosphoric acid salt; and a process for producing a slow-releasing nitrogenous fertilizer which comprises subjecting the resulting methylol urea solution to dehydration condensation and drying the resulting condensate are disclosed. The methylol urea solution undergoes no substantial pH variation with time either during or after the addition reaction, and the fertilizer obtained therefrom is excellent in slow-releasing properties.
HYDROXYMETHYL DERIVATIVES OF UREA AND FORMALDEHYDE: CONDITIONS OF THEIR FORMATION.
Bulygina,Gritsenko,Sokolovskaya,Sarbaev
, p. 419 - 421 (2007/10/02)
The polycondensation process may be represented in the form of a reaction between functional groups, with formation of monohydroxymethylurea (I) and dihydroxymethylurea (II). Formation of these derivatives depends on the PH, temperature, and excess of formaldehyde of urea. When the reaction is conducted in a weakly alkaline medium, either mono- or dihydroxymethylurea is formed. Formation of monohydroxymethylurea does not go to completion in an alkaline medium, as the reaction is reversible. The reaction can be shifted toward increase of the monohydroxymethylurea yield by the use of excess formaldehyde. On the basis of their investigations the authors propose specific conditions for preparation of pure mono- and dihydroxymethylurea. The synthesis is based on the reaction of urea with formaldehyde in aqueous solution containing 44 mass % of water at 1:1 molar ratio of urea to formaldehyde for formation of monohydroxymethylurea, and 1:2 molar ratio with 5% excess of formaldehyde over the stoichiometric ratio for formation of dihydroxymethylurea.
Canonical Chemical Theories Exemplified by the Mehtylolation of Urea and Melamine
Gebregiorgis, Taddesse,Gordon, Manfred
, p. 359 - 382 (2007/10/02)
Old and recent data on equilibria and kinetics of methylolation of urea and melamine are analysed.The theoretical framework affords a sequence, claimed to be canonical of successive phenomenological approximations.The theory, expounded earlier, begin with two successive schemes whose essentials go back to early work by Pauling and by Flory.The two stages here suffice to show that all the data from eight laboratories, covering the six-membered family of methylol ureas and rhe ten-membered family of methylol melamines, are in quantitative agreement, a circumstance unsespected by other workers in the field.The statisticalthermodynamic and kinetic principles involved are therefore expounded in more detail than before.Using them, very small substituent effects (e.g O.35 kJ kol-1 are deduced with high significance and accuracy.Owing largly to the recent measurement by Tomita, the methylol melamines are claimed currently to be the thermdinamically best characterised family in the chemical literature.A challenge arises for theoretical chemists to test quantum-theoreticaltechniques against the measured energetics of substituent effects in this family, and to exploit for other families the graph-theoretical analysis of molecular additivity which underlies the approximation schemes, which already well tested.
