Reasons and Solutions for Printing Adhesion of PVC Calendered Film (I)

PVC calendered film is printed on the PVC calendered film by intaglio printing machine. The film has clear patterns, colorful colors, variety of types, and strong decorative effect. It has applications in daily life, military and industry. However, after the printing, such as film adhesion phenomenon, will greatly affect the decorative effect of the product, reduce product quality, which is often plagued PVC calendar printing film production of a major problem. Through the actual observation and analysis of production and practice, this paper puts forward the causes of the phenomenon and the improvement methods.

1 Analysis of the reasons for film adhesion after printing

There are two main reasons for PVC calender film printing adhesion: First, the quality of the base film is not stable, and second, the ink fineness and formula are unreasonable. The specific situation is analyzed as follows.

1.1 The base film is soft

The amount of plasticizer in the PVC calendered film is too large, the base film is soft, especially when the base film is poorly plasticized, the plasticizer in the base film migrates to the ink layer, and the vinyl chloride-vinyl acetate resin in the printing ink softens. Causes adhesion. The softer the base film, the more pronounced this phenomenon is.

1.2 base film tight side belly

Bottom film refers to the phenomenon that the two sides of the calendered film are tight and loose in the middle. When the film is unwound, drawn, printed, or wound, it is necessary to increase the tension adjustment accordingly, so that the film is flat, and the accuracy and flatness of printing, color registration, and take-up are improved, so that the film is internally generated after winding. Larger pressure can easily cause film sticking.

1.3 Insufficient ink fineness

The ink fineness that satisfies the printing needs is generally less than 30μm, and the fineness of the colorant that our factory prepares by oneself is often greater than 50μm. The ink fineness is not up to the requirements, which can easily cause a series of problems, such as emptiness, expansion, stencil printing, poor coloring, and low color fastness (only 3 to 4 grades). At the same time, in order to meet the customer's requirements for printing color, ensure the coverage and vividness of the ink, and unconsciously increase the proportion of pigments and increase the engraving depth of the printing roller (40 lines for the mesh line), not only the consumption is serious, but also the cost. Increasing, the printing process is difficult, the color is rough, not full, and it is easy to cause the ink not easy to dry; at the time of rewinding, although the surface of the ink layer has dried up, there is still a solvent inside, and these solvents will slowly develop with the passage of time. Exudation, softening the surface of the ink layer has dried, and eventually appear viscous phenomenon, especially in the face of large ink color, in the current process conditions, it is more difficult to completely dry and sticking phenomenon.

1.4 Ink Composition and Formulation

PVC printing ink is mainly composed of resin, solvent, coloring agent and plasticizer. If the formula is not reasonable, or it cannot be carefully adjusted according to the climate and specific conditions, it will cause the ink to dry slowly and cause sticking. In fact, there are many factors that affect the adhesion phenomenon of printing film, such as drying method, drying temperature, air flow speed, printing speed, etc. These factors belong to the process adjustment problem, this article will not be discussed one by one.

2 Printing film adhesion improvement method

2.1 Quality Control of the Base Film

As mentioned before, the quality of the base film is directly related to whether the printing film is stuck or not. Therefore, it is very important to strictly control the quality of the PVC film. If the film is found to be soft, care should be taken to control the amount and type of plasticizer in the base film. The amount of lubricant should not be too much. At the same time, observe if the temperature of the calender roll is too high; Inconsistent shrinkage, we must first check whether the film has a "three high and two bottom" phenomenon, whether the roller temperature is even, and whether the shaft crossing angle is too large; then check whether the cooling is even, whether the coiling tension is appropriate and stable, and the rolling speed ratio Is it reasonable to wait? And the bottom film is as cold as possible. Only by reasonably determining the calendering film formula and calendering process conditions can ensure the quality and performance of the base film to be stable, thereby bringing convenience to the subsequent printing process, ensuring the printing quality and avoiding the sticking phenomenon.

(to be continued)