Reasons and Solutions for Printing Adhesion of PVC Calendered Film

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.

 
2.2 reasonably determine the ink composition and formula

PVC printing ink is made of transparent pulp and color paste mixed in a certain proportion. When used, it is diluted with a mixed solvent to the required viscosity. The amount and type of plasticizer and solvent used in the ink composition have an important influence on the sticking phenomenon of the printing film. In general, the effects of the selected materials on the dissolving power of the chloroacetic resin, the wetting and penetrating ability of the base film, the viscosity adjusting ability, and the drying speed should be comprehensively considered. Usually plasticizers choose DBP as well. DBP has high plasticizing efficiency, strong volatility, and easy drying. The solvent is generally cyclohexanone, butyl acetate, acetone, and ethyl acetate. It is often used as a mixed solvent.

2.3 To improve the color paste fineness and uniformity of solid-liquid dispersion

As mentioned earlier, the ink fineness has a very important influence on the printing adhesion, and the fineness of the ink depends on the fineness of the colorant. In the process of color matching paste, the components must be fully mixed and homogenized, and then ground to a certain degree of fineness with a colloid mill. Generally, the color paste particles are controlled below 30 μm. Paste grinding can use the process route shown in Figure 1.

In the grinding process should pay attention to: 1 colloid mill must pass water cooling; 2 circulation pump I, II flow and colloid mill fineness should be adjusted consistent; 3 colloidal fineness can be adjusted according to production needs and different varieties of raw materials, a can The paste must be colloid milled 3 times (ie, coarse, medium, and fine) for production.

The color paste is grinded by this method, the fineness and dispersion degree are greatly improved, and the proportion of the pigment in the color paste can be reduced. This not only reduces the cost, but also improves the fluidity of the color paste, is easy to produce, and avoids sizing and paste sticking. At the same time, the printing roller engraving depth can be reduced, increase the network cable and reduce the slurry consumption per ton of film. In this way, product color strength and color fastness improve, ink full, delicate color, bright, easy to dry and completely completely avoid the phenomenon of stickiness after the roll is not open, so that the quality of PVC printing film has been greatly improved.