| 摘要 |
Aqueous melamine-formaldehyde condensates having a molar ratio of greater than 1.5 are obtained by reacting melamine and formaldehyde if formaldehyde and melamine are reacted in the first step in a molar ratio of at least 1.55 in aqueous solution at a pH above 7 at least to the commencement of water-incompatibility, at least 5 mol %, based on the melamine already present, of melamine in solid form are added at the reaction point, and the reaction is continued until the added melamine has dissolved, the first step of the reaction of formaldehyde and melamine advantageously being carried out in the presence of a salt from the group consisting of the alkali metal sulphites, hydrogen sulphites, disulphites, sulphoxylates, phosphates, polyphosphates and borates.
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