When BOPP is used in foods, calendars, albums, adhesive tapes, etc., it often requires printing, coating, bonding, etc. Because the surface tension value of polypropylene material itself is relatively low, only 31 dyne, and in When applied to the above aspects, it is generally required that the surface tension strength of the film is more than 38 dyne. Therefore, in the production of BOPP, it is often required to perform surface treatment on the film to increase its surface tension and improve the adhesion and wetting of the polymer. Sex to meet the requirements of use.
There are two commonly used surface treatment methods: one for corona treatment and the other for flame treatment. The principle of corona treatment is that the film passes between the two electrodes with high pressure. The high pressure causes ionization of the air between the electrodes and generates electron flow between the electrodes. An oxidized polarizing layer is formed on the surface of the film to make the surface of the film polar, which facilitates printing. Ink adsorption; flame treatment is the use of a specific torch, burning a certain composition and ratio of gas and air, the formation of temperature up to 2100 ~ 2800 °C oxidizing flame, to achieve the purpose of changing the surface properties of the film in an instant, in the actual processing process The temperature of the flame, the distance between the flame and the film, and the processing time are important factors affecting the treatment effect. In practical applications, BOPP equipment manufacturers basically use this method because corona treatment is simple and easy, and the treatment effect is good. The following is a discussion on the testing, control of the corona treatment on BOPP processing, and the effect on the performance of the film.
1.1 Determination of corona treatment strength of BOPP film
The test method commonly used for the surface tension of BOPP film is the coating method. The principle is to use the two liquids formamide and ethylene glycol to mix in different proportions to obtain a series of test solutions with different dyne values ​​(see table a) During the operation, the test liquid is applied on the surface of the film. The dyne value corresponding to the test solution that breaks at the liquid surface for 2 seconds indicates the corona treatment intensity of the film.
As a three-layer co-extruded tobacco film, the main ingredient of the surface layer is a self-adhesive polypropylene copolymer. At present, BOPP heat sealing materials commonly used at home and abroad mainly include polypropylene random binary copolymer (ethylene/propylene copolymer). Such as SOWAY KS413, Montel PLZ697, CHISSO XF7511, etc., random terpolymers (propylene/ethylene/butene copolymers) such as Solvay KS309, Sumitomo SP89 E-1, Montel EP3C39F and mixtures (terpolymers with butenes Mixture) such as Schulman IS2739, these three heat seal materials have their own characteristics, they have different effects on the heat seal performance of the smoke film.
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