ON THE CHEMICAL TREATMENT OF THE STARCH FOR PAPER COATING

I. OXIDIZED STARCH BY CALCIUM HYPOCHLORITE

Abstract

As the glue for paper coating, important requirements are high adhesive strength and good flow characteristics. When we use the starch for coating, native starch are not good flow, so that must dilute by plerty of water, consequently adhesiveness degrade. Chemically oxidized starch may be prepared in a large of viscosities depending on the degree of oxidation and optimum viscosity have desirable adhesive strength.
(1) Liquid ratio for starch : 1 : 1
Temp of oxidation : 25°C
Calcium hypochlorite (as available chlorine) : 1.41.6%
Sodium bisulfite 34%sol 0.43%
Sodium hydroxide for starch : 0.4%
Cooking temp, and time : at 90°C, 15 minutes.
Viscosity of glue : 1.25
(2) Manufacture of coating mixture.
Starch of Sweet Potato 100kg
Bleaching so (contain 1.41.6%, Av. cl in it) 100kg
Reaction at 25°C, 45 hrs on stirring. When available chlorine residue attain to 0.1% add 34% NaHSO₃ sol, 0.5kg. And add 0.4kg of NaOH, cook it at 90°, 15 minutes. In warm glue mix clay or other pigments and make mixture content 3336. After coating and drying, through 2 rounds to supercalender of lines pressure 9, 700 kg/100 cm and tests printing adaptation. Their result shows next table.
Optimum requirement of oxidized starch for printing strength are 2023% on relief and offset printing. For collotype printing, oxidized starch glue are not suitable, because of weak water resistance on the experiments of this time.
We wish to announce on improvement of water resistance at other time.