PROBLEM TO BE SOLVED: To aim at the improvement of the freezing point and hardness in a fatty acid-based soap having a large ratio of potassium as a counter ion.SOLUTION: A solid soap containing sodium and potassium as counter ions of a fatty acid, and having ≥20 mol% potassium in the counter ions is characterized by including 1 to 5 mass% betaine. Especially trimethylbetaine has an excellent freezing point elevation activity, and the solid soap is provided by containing 1 to 5 mass% trimethyl glycine within Na/K=80/20 to 50/50 range.COPYRIGHT: (C)2013,JPO&INPIT【課題】対イオンとしてカリウムの割合の大きい脂肪酸石鹸系石鹸において、凝固点及び硬度の向上を図る。【解決手段】脂肪酸の対イオンとしてナトリウム及びカリウムを含み、対イオン中、カリウムが20モル%以上である固形石鹸において、ベタインを1~5質量%含むことを特徴とする固形石鹸。特にトリメチルベタインには優れた凝固点上昇作用があり、Na/K=80/20~50/50の範囲で、トリメチルグリシンを1~5質量%含む固形石鹸。【選択図】なし
