Studies on formaldehyde condensation resins. XIII. Gelation of acetoguanamine–formaldehyde resin

<jats:title>Abstract</jats:title><jats:p>The gelation reaction of acetoguanamine with formaldehyde was investigated in the light of the gelation theory for tetrafunctional amino resins described in the previous paper. The gel time and extents of reaction of formaldehyde, amino groups, and imino groups varied with the molar ratio in the feed, but values of <jats:italic>K</jats:italic> (the ratio of the rate constant for condensation to that for addition) and <jats:italic>k</jats:italic> (the ratio of the rate constant for addition of the imino group to that of the amino group) were nearly constant. When the catalyst concentration was increased, the gel time, extents of reaction of each functional group, and the values of <jats:italic>K</jats:italic> and <jats:italic>k</jats:italic> varied; in particular <jats:italic>K</jats:italic> increased markedly. From the results of varying the molar ratio and concentration of acidic catalyst, it was found that the number of methylol groups per molecule of acetoguanamine at the gel point was influenced by the reaction conditions but the number of methylene linkages per molecular of acetoguanamine was nearly constant at about 0.6, regardless of reaction conditions. The number‐average molecular weights up to the gel point varied with the reaction conditions, but at the gel point they were all nearly constant at about 385.</jats:p>