[OH-].[Na+].C=O.[N:5]1[C:12]([NH2:13])=[N:11][C:9]([NH2:10])=[N:8][C:6]=1[NH2:7].C(O)(=O)[C:15](O)=[O:16]>CO>[N:5]1[C:12]([NH2:13])=[N:11][C:9]([NH2:10])=[N:8][C:6]=1[NH2:7].[CH2:15]=[O:16].[CH3:15][OH:16]0.6 part of a 25% strength by weight aqueous sodium hydroxide solution was added to 783 parts of 40% strength by weight aqueous formaldehyde solution, after which a pH of 8.3 resulted. After the addition of 0.5 part of Borax, 170 parts of melamine were metered in. After heating to 80° C., the mixture was stirred at said temperature until the contents had reached a milky turbid consistency. 777 parts of methanol were added and the temperature was brought to 68° C. After the addition of 2.9 parts of oxalic acid, the pH was 3.8. Stirring was carried out at 68° C. for 20 minutes, the solution becoming clear. After the addition of 11.0 parts of a 25% strength by weight aqueous sodium hydroxide solution, a pH of 7.8 resulted. About 1250 ml of methanol/water were distilled off between 60 and 100° C. After 100° C. had been reached, stirring was carried out for a further 10 minutes at this temperature. After application of reduced pressure of about 80 mbar, a further 60 ml were distilled off, the internal temperature decreasing to 50° C. The viscosity was brought to 200-350 mPa.s by adding 57 parts of demineralized water. 585 parts of resin (melamine/formaldehyde/methanol=1/5.3/3.4) were obtained.
Wird geladen…
