TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Method: The preparation isobutylene hydantoin comprises in a reactor, adding water, hydantoin, 29-33% industrial caustic soda and monoethanolamine, heating to clarify, dropwise adding isobutyraldehyde, refluxing for 8-12 hours, cooling to room temperature, dropwise adding 34-37% hydrochloric acid to adjust the pH to 4.5-6, then cooling to 8-10 degrees C, stirring for 70-100 minutes, filtering, and drying. In step (i), the weight ratio of water and isobutylene hydantoin is 2-4:1, industrial caustic soda and isobutylene hydantoin is 3-3.6:1, calcium chloride solution and isobutylene hydantoin is 0.9-1.2:1, and the heat refluxing time is 80-100 minutes. In step (ii), prior to adding hydrochloric acid, the filtrate is cooled to 45-55 degrees C. The method comprises (i) in a reactor, adding 300 kg water, 78 kg hydantoin, 5 kg (30%) industrial caustic soda and 9 kg monoethanolamine, heating to clarify, dropwise adding 56 kg isobutyraldehyde, refluxing for 8-12 hours, cooling to room temperature, dropwise adding 36% hydrochloric acid to adjust the pH to 5, then cooling to 8-10 degrees C, stirring for 90 minutes, filtering, and drying to obtain isobutylene hydantoin; (ii) heating 240 kg drinking water and 267 kg 30% industrial liquid caustic soda mixed solution into a reactor, purging with nitrogen three times, refluxing for 90 minutes, cooling to 80-90 degrees C, adding isobutylene hydantoin 78 kg, heating and refluxing for 90-100 minutes, dropwise adding 40% 85.8 kg calcium chloride aqueous solution, stirring for 10 minutes, filtering while hot and collecting the filtrate; (iii) cooling the filtrate to 48 degrees C, adjusting the filtrate pH to 1.8 with 36 mass.% hydrochloric acid, and passing nitrogen under vacuum 2-3 times; (iv) adjusting the pH to 8.05 with 30% industrial caustic soda, cooling to 35 degrees C, and adding 100 kg calcium chloride solution (40%), insulating for 60 minutes, cooling to 6 degrees C, stirring for 120 minute, and filtering the crude product; and (v) under nitrogen atmosphere, refluxing purified water for 50-60 minutes, adding 74 kg ketone leucine calcium crude product and 1 kg 767 charcoal, decolorizing and refluxing for 60 minutes, filtering while hot, dissolving the filtrate, stopping heating, cooling to 3-8 degrees C, stirring for 90 minutes, filtering, and drying. Preferred Components: The weight ratio of: water to hydantoin is 3-4:1, industrial caustic soda to hydantoin is 0.04-0.07:1, ethanolamine to hydantoin is 0.1-0.2:1, and isobutylaldehyde to hydantoin is 0.55-085:1. In step (iii), the weight ratio of calcium chloride solution and isobutylene hydantoin is 1.1-1.5:1. In step (iv), the weight ratio of purified water to dry crude product is 11-16:1.