When the resin are saponificated by Na₂CO₃ with high temperature and long time, there appears wrong color in the resin soap, and remains unfavourable color in the paper when are used as sizing matter.
We are carried several experiments about to avoid their color. First, we recognized that short time cooking by NaOH with high temperature was effective to avoid contamination and at the same time adding Superite (Sodium Sulfoxylate formaldehyde) with NaOH was more effective. Namely, Superite are decomposed to SO₂ and CH₂O at about 100°C, these strong reduction power are active to avoid wrong color. This Chemical is alkali side, so that sizing agent are not injured.
We got the following formula in the experiments as test method :
resin : color number 60-125
NaOH : about 10% for resin
Superite : 50% for resin
Liquor ratio : 1 : 1 (for solid)
cooking time : 1 Hr.
The size from these conditions are approximately same grade compare with pale color resin (color number 15)
As other chemicals, Na₂SO₃ are not effect on bleaching power and H₂O₂ NaCLO injures size agent.
On low temperature saponification, Delthirna method are effective to pale grade color resin to more prevent contamination of paper. But of all experiments, most effective method was Superite method in high temperature with short time cooking.