Brief analysis of the characteristics and applicat

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A brief analysis of the characteristics and application methods of protective glue

protective glue is a kind of transparent glue composed of natural glue or synthetic glue, which can protect the graphic and non graphic parts of the printing plate and prevent the oxidation and dirt of the plate. Therefore, we hope to strive for more central supporting funds to support this kind of liquid earlier. Common protective adhesives include Arabic gum and new synthetic resin lotion interior wall coating gb/t 9756 ⑵ 001 polymer adhesive

1. Characteristics of protective glue

(1) easy to decay. In the hot environment (the use temperature of Arabic gum is - 5 ℃ ~ 45 ℃), yeast is easy to reproduce and ferment in Arabic gum liquid, which makes Arabic acid free and changes the colloidal property. This is the general property of sugars, and also the reason why Arabic gum foam and its use time will be rotten. With the increase of temperature, the acidity will increase, the corrosiveness to the metal plate will increase, and it is easy to drop the plate. In serious cases, Al2O3 will fall off. This should be paid special attention in summer to keep the protective glue away from high temperature

(2) hydrophilicity. The molecular structure of gum Arabic is composed of -cooh and -oh linked to the same hydrocarbon bond. These two functional groups are hydrophilic, and hydroxyl (-oh) is easier to accept water than carboxyl (-cooh). Therefore, when Arabic gum is dissolved in water, it will dissolve for about 72 hours according to the process of diffusion, water absorption and swelling to form a molecular solution of the dispersion system. The cylinder hydraulic tester is called to test the gas cylinder, and the hydroxyl in each molecule shows great hydrophilicity. It can automatically dissolve in water into a single-phase stable system, which will neither condense nor precipitate, and can ensure the stability of the dispersion system for a long time

(3) weak acidity. Because peach gum contains Arabic acid (xcoh), its aqueous solution is weakly acidic. It neutralizes with alkali, reacts with metal or metal oxide to form arabite, releases hydrogen, and has good adsorption

2. The function and application method of protective glue

can improve the hydrophilicity of non graphic parts, prevent dirt on printing, protect the layout and prevent scratches

manual gluing: use collagen solution and water at a dilution of 1:1. Pour an appropriate amount of glue (about 45ml per square meter) onto the layout, and then apply it evenly with cellulose sponge. Wipe the excess glue with a dry cloth, and then dry it

machine gluing: use collagen solution and water to dilute by 1:3. The drying temperature should be controlled below 70 ℃, generally 60 ℃ ~ 65 ℃

special note: the glue applicator without supplementary structure should be replaced every three days. For the first time, youbu has synthesized polyazo phenol mesoporous materials in aqueous phase system. The glue applicator with filling structure should be replaced once a week. The lower the concentration of protective glue, the better the inking performance during printing, but it is easy to bruise and get dirty. On the contrary, if the concentration of protective glue is too high, it is easy to cause poor inking

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