The production process of hydroxypropyl starch ether (HPS) mainly involves the etherification reaction of starch with propylene oxide under alkaline conditions. Depending on the solvent system, it can be divided into three mainstream processes: wet process, dry process, and solvent process. Among them, the solvent process is widely used due to its superior product performance.
Core Reaction Principle:
The preparation of hydroxypropyl starch ether is essentially an etherification reaction: Under the action of an alkaline catalyst such as sodium hydroxide, the hydroxyl groups (-OH) in the starch molecule undergo a ring-opening reaction with propylene oxide to generate hydroxypropyl substituents (-OCH₂CHOHCH₃), thus forming modified starch with better water solubility and stronger stability.
Main Production Process Classification:
Solvent Method (Organic Solvent Method) – Mainstream High-Quality Process
Process Characteristics: Starch is dispersed in organic solvents such as ethanol, methanol, or isopropanol, and an alkaline catalyst and propylene oxide are added. The reaction is carried out in a closed system at 40–50℃.
Advantages: Uniform reaction, high degree of substitution and more uniform distribution; High product purity, easy to filter, wash and dry; Continuous production, suitable for large-scale industrial preparation.
Typical parameters:
Starch: 10 parts (mainly corn starch)
Propylene oxide: 3.5 parts
Sodium hydroxide: 1.2 parts
Ethanol: 50 parts (as diluent)
Reaction temperature: 40–50℃, time: approximately 24 hours
This method effectively inhibits starch granule swelling, avoids gelatinization, and ensures efficient reaction at the molecular level.
