| 摘要 |
PROBLEM TO BE SOLVED: To increase viscosity, and thereby solve problems such as the deterioration of wiping properties or gum removing properties by preparing a printing plate protecting agent used for protection of a printing plate for lithography with the addition of gum arabic and an organic reducing agent. SOLUTION: When manufacturing a printing plate protecting agent for a lithographic printing plate, rubber arabic and an organic reducing agent are added. In this case, the gelation of the printing plate protecting agent is prevented from occurring by using the rubber arabic with a moisture content of not more than 15%. Further, if the rubber arabic with a moisture content of 15% or more needs to be used, the gelation can be prevented from occurring by preparing the printing plate protecting agent at 60 deg.C or higher. Besides, it is preferable that as the organic reducing agent, a combination of 3- pyrazolidons and dihydroxybenzenes, a combination of aminophenols and dihydroxybenzenes or a combination of 3-pyrazolidons and ascorbic acid or a combination of aminophenols and ascorbic acid be used. This organic reducing agent is usually used at a dose of 0.001-1.4mol/l. |
