Hydroxypropyl Starch For Preparing Empty Capsules And Hydroxypropyl Starch-Based Soft Capsules

A method for preparing a hydroxypropyl starch, comprising:

• (1) taking 1 part of a starch and 3 to 8 parts of an ethanol, placing the starch and the ethanol into a reaction tank, and stirring rapidly to disperse the starch to form a starch dispersion;
• (2) taking 0.05 to 0.2 parts of a catalyst for an etherification reaction, and slowly adding the catalyst to the starch dispersion in the reaction tank;
• wherein during the addition of the catalyst, stirring is done rapidly and after the addition is complete, stirring continues quickly for 20-40 minutes;
• (3) taking 0.1 to 0.3 parts of a propylene oxide and slowly add the propylene oxide to the reaction tank;
• wherein after the addition of the propylene oxide is complete, closing the reaction tank and continue stirring, then raising a temperature in the reaction tank to 30 to 50° C., and controlling the pressure in the reaction tank at 0.1 to 0.3 MPa;
• wherein the reaction occurs for 0.5 to 2.5 hours to form a reacted product;
• (4) adding the reacted product to cold water at 20 to 25° C., 5 to 10 times a weight of the reacted product, soaking and stirring for 8 to 10 hours;
• wherein after a gum of the reacted product is dissolved in water, adding a strong acidic cation exchange resin to neutralize, and stirring until pH is 6.0-7.0 to form a filtrate, and wherein the filtrate is a highly substituted hydroxypropyl starch solution;
• and
• (5) heating the hydroxypropyl starch solution in a jacketed open pan, and slowly stirring as temperature is increased, and the solution becomes turbid heating the hydroxypropyl starch the solution to 30-60° C. for flocculation and formation of a micelle;
• wherein a propyl starch gum product is vacuum dried and pulverized into a solid powdery product.