The anti-adhesion knowledge of Gift Box is here

The anti-adhesion knowledge of Gift Box is here!

Blocking refers to a sticking phenomenon between the contact layers of plastic films. There are two kinds of sticking phenomenon: One is that the printing surfaces stick to each other. The second is that the ink layer of the printed matter adheres to the other contact surface, or the ink adheres to the other contact surface.

The first phenomenon is that the films stick to each other, the bag mouth is difficult to open, and the user refuses to use it. The internal sticking can be effectively prevented by adding slip agent and opening agent to the resin.

The second phenomenon is that the roll material cannot be unwound smoothly, which seriously hinders high-speed line production or damages the printed pattern and contaminates the contact surface due to ink peeling. In severe cases, the films cannot be torn apart and cannot be used, resulting in product scrap. Therefore, how to control and improve the anti-adhesion of the ink in the gravure printing process is very important.

(1) Features of anti-adhesion products

The anti-adhesion product should have the following characteristics: ①The material roll is unwinding smoothly and the running performance is good, so as to adapt to the production of high-speed packaging; ②The surface is smooth and the package opening is good.

(2) Substrate selection of anti-adhesion products

In the gravure printing process, "adhesion" is related to a series of factors such as substrate smoothness, ink adhesion, solvent volatilization speed, operating environment, printing drying conditions, and printing speed. The selection of the substrate should fully consider the above factors, and should have the characteristics of good printing adaptability, strong ink adhesion, and good solvent release. Common substrates include BOPP film, BOPET film, aluminum foil, PT film, etc., and the ink, solvent and printing process parameters that match the substrate are selected.

(3) Special technical indicators

In gravure printing, the anti-blocking property of the printed matter is mainly improved by improving the anti-blocking property of the ink. Therefore, the anti-blocking requirements must be based on factors such as the type of binder resin in the ink, the amount of solvent residues, and the parameters of printing equipment, and the anti-blocking requirements to be achieved through the design of materials and properties.

(4) Specific printing process

Taking the anti-blocking printed matter as an example, the following points should be paid attention to when designing the printing process: 1. The ink made of high softening point binder resin should be selected, which is beneficial to prevent blocking. Correspondingly, the solubility and release of the solvent to the resin should be better; (2) it is necessary to ensure that the printing ink layer is fully dried to control the residual solvent, so as to reduce the possibility of adhesion between the printed matter; , after winding, the back side has a strong affinity for contacting the ink layer, and the anti-blocking property is poor. Therefore, during printing, the corona treatment method should be adjusted, single-sided treatment should be performed, and the printing speed should be slow. After printing, it must be fully cooled by cooling rollers before winding.

(5) Anti-stick test method

The anti-blocking test of gravure prints is carried out in accordance with the provisions of GB/T13217.8-2009 "Inspection Method for Gravure Plastic Ink-Anti-blocking Test".

1) Principle: The obtained ink film imprint is folded and contacted in half within a specified time, and under a certain temperature and pressure, after a certain period of time, the adhesion of the imprint is observed.

2) Inspection conditions: The inspection should be carried out under the condition of (50±1)℃.

3) Inspection steps: ① Prepare the sample by printing the ink on the printing substrate, or by scraping the sample with a wire rod on the printing substrate; ② After placing the printed sample for 2 minutes (for example, the printing sample film is printed with water-based ink, It needs to be dried in an oven at 59~61℃ for 5min, taken out and cooled), folded between the two pieces of glass on the upper and lower circles, put it in the oven at 49~51℃, and put a 2000g weight on it. The code is placed for 2h; ③Take it out, open the folded part, depending on its adhesion.

4) Test result: Cover the pressed part with translucent millimeter grid paper with a width of 20mm. Count the number of grids occupied by the ink layer and the number of grids occupied by the removed ink layer. Calculate as follows

B (%)=B1/(B1+B2)×100

In the formula, B——the degree of ink adhesion

B1——The number of grids of the ink layer

B2 - the number of grids of the removed ink layer

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