Recent Developments in the Chemistry of Cross-Linking Agents

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Abstract
Kinetic and thermodynamic studies of the reaction of urea with formaldehyde have led to a technically feasible synthesis of hitherto unknown trialkoxymethyl ureas, particularly trimethoxymethyl urea. Fabrics cured with trimethoxymethyl urea exhibit better resistance to acid hydrolysis than those finished with dimethylol urea. Reactivities, hydrolysis stabilities and other applied properties are described in relation to various reaction parameters. Investigations of the equilibrium states and formation and dissociation constants led to the discovery that, when a monocarboxylic acid amide is reacted with at least two molecules of formaldehyde in highly concentrated solutions, dime thylol compounds can be converted in high yields, by acetalation with alcohols, to the stable N, N-dialkoxymethyl mono carboxylic acid amides. Chlorine-and hydrolysis-resistant, nonwrinkling finishes can be obtained with the N,N-dimethoxy methyl monocarboxylic acid amides just like the dimethylol carbamates. Methylol compounds of 4,5-dihydroxyethylene ureas and of 4-hydroxy (alkoxy)-5, 5-dialkylpropylene ureas occupy a special position, since not only the methylol groups, but also the ring hydroxy or alkoxy groups can be substituted by O- cellulose residues under certain reaction conditions. 4,5-Dihydroxy (alkoxy)-ethylene ureas undergo conversion reactions in acid media, particularly at elevated tempera tures, and hydantoin derivatives and strongly colored intermediate products are formed after passing through the 4-hy droxy (alkoxy)-imidazolone stage. While the 4,5-dihydroxy (alkoxy)-ethylene ureas are practically useless for a wrinkle-free finish, and their monomethylol compounds are only conditionally suitable, finishes with good characteristics can be achieved with the monomethylol compounds of 4-hydroxy (alkoxy)-5.5-dialkylpropylene ureas. The kinetics and reaction mechanisms of curing with 4, 5- dihydroxy (alkoxy)-ethylene ureas and with 4-hydroxy (alkoxy)-5,5-dialkylpropylene ureas in relation to various reaction parameters are discussed in detail. Finally, the kinetics and mechanisms of crosslinking with N-methylol compounds are briefly considered.