Method for manufacturing high-cationic starch solutions

Abstract

A method for producing starch solutions of high cation equivalent value with a DS of 0.1-1.0) is provided. The starch to be cationized is slurried to form a suspension of about 10-80% solids content in an aqueous mixture of a cationizing agent. In the cationization chlorohydrin-functional cationizing agent is used by about 90-1100 g per kg starch solids, and a catalyst is added to the slurry. The reaction is carried out at a high solids content of 40-80% in at least two steps, in the first of which a temperature of about 5-40° C. in maintained, and in the second step a temperature of about 70-180° C.

1 . Method for preparing starch solutions of high cation equivalent value (with a DS value of 0.1-1.0), in which method the starch to be cationized, preferably an oxidized starch, is slurried to form a suspension of about 10-80% solids content in an aqueous mixture of a cationizing agent, the cationizing agent, such as 2,3-epoxypropyltrimethylammonium chloride or an equivalent chlorohydrin-functional cationizing agent being used by about 90-1100 g per kg starch solids, a catalyst is added to the slurry, and the cationizing agent is reacted with the starch, characterized in that the reaction is carried out at a high solids content of 40-80%, preferably 50-60%, in at least two successive steps, in the first of which a temperature of about 5-40° C. is maintained, and in the second step a temperature of about 70-180° C.  
     
     
         2 . Method according to    claim 1   , characterized in that the first reaction step is carried out at a temperature of about 15-35° C. and a reaction solids content of 40-80%, preferably 50-60%.  
     
     
         3 . Method according to    claim 1    or    2   , characterized in that the first reaction step is carried out during a time of about 1-10 h, preferably about 3-6 h.  
     
     
         4 . Method according to    claim 3   , characterized in that the first reaction step is carried out to a relative proportion of about 30-75% of the total reaction.  
     
     
         5 . Method according to    claim 1   , characterized in that the second reaction step is carried out at a temperature of about 80-140° C. and a reaction solids content of 40-80%, preferably 50-60%.  
     
     
         6 . Method according to    claim 5   , characterized in that the temperature of the reaction mixture is elevated for carrying out the second reaction step by using a high energy intensity, such as steam heating, preferably direct steam heating.  
     
     
         7 . Method according to claims  4 ,  5 , and  6 , characterized in that the temperature of the reaction mixture is elevated for the second reaction step by using an energy intensity, whereby the relative proportion of the reaction progress during said temperature elevation stage is 20-60%.  
     
     
         8 . Method according to    claim 7   , characterized in that the cationization reaction is completed at a decreasing temperature in a third step, immediately subsequent to said second step.  
     
     
         9 . Method according to any of    claims 1    to    8   , characterized in that as a catalyst an alkali or earth alkali metal hydroxide is used in an amount of about 1-4%, preferably about 2-3% of the amount of starch.  
     
     
         10 . Method according to claims  8  and  9 , characterized in that said third step is carried out in less than about 8 h, preferably during about 1-2 h.