Synthetic paper

After the 1960s, due to the depletion of pulp resources and the development of the petrochemical industry, synthetic papers came out one after the other in 1967.

The so-called synthetic paper, simply said: The synthetic polymer material as the main raw material, through the processing, gives the properties of the paper, and can be used as paper in paper applications.

Synthetic paper was originally made of a foamed plastic such as polystyrene to produce a sheet or a film-like material with the properties of paper. So far, after continuous improvement, there have been so-called synthetic pulp products. Synthetic papers also use a variety of synthetic polymers to suit various current printing methods.

A paper processing of synthetic paper

The surface of natural paper has a certain degree of absorption. After the ink is printed on the surface of the paper, some of the components can immediately penetrate into the pores of the paper and then solidify. For the synthetic paper to have its surface absorb ink, it must be processed. The main methods are as follows:

(1) Filling. Titanium dioxide, calcium carbonate and other fillers themselves are very tolerant to printing inks, but only adding about 20% to 30% of the filler, and can not obtain permeability, because at this time, the polymer is covered around the filler, there is not enough Capillary. Only by adding a sufficient amount of filler or washing off the surface layer with a solvent to expose the filler can a certain permeability be obtained.

(2) fill and extend and use. When a polyolefin film containing a large amount of filler is stretched, fine cracks are generated. Helps ink penetration.

(3) Pigment coating. The clay, titanium dioxide, calcium carbonate and the like are coated on the surface of the synthetic paper together with the adhesive, and the principle is the same as that of the coated paper and coated paper in the natural paper. With this method, not only can the same permeability as natural paper be obtained, but also the smoothness is excellent, and the ink acceptability and printing effect over the natural paper can be obtained.

Second, the characteristics of synthetic paper

Table 1 lists the properties of synthetic paper and natural fiber paper.

From Table 1, it can be seen that the synthetic paper has good whiteness, gloss, smoothness, light resistance, and dimensional stability. In addition, since synthetic paper is a paper made from a polymer synthetic material, it has thermal plasticity. It will not be like natural paper, it will cause hair failures, will not produce dust, and is very effective for clean rooms. Thanks to its good water resistance, it is best suited for printing advertising posters, travel maps, park tickets, museums, and exhibition tickets that are easily wetted by water. For example, admission tickets for the National Palace Museum are printed on synthetic paper, and the pattern printing is very sophisticated and very meaningful.

So far, the price of synthetic paper is higher than that of ordinary paper. Although the strength of synthetic paper is large, it is easy to tear when there is a break. After the ink dries, the paper surface is easy to bulge, and the multicolor overprinting is poor. The degradation treatment of waste paper has not been completely resolved. Therefore, the development of synthetic paper is still relatively slow, but from the perspective of protecting forest resources and environmental protection, the development prospects of synthetic paper are very optimistic. Some paper mills in the world invest funds to improve the printability of synthetic paper and increase The size of large synthetic paper reduces costs to accommodate high-speed, multi-color printing.

Third, synthetic paper in the printing should pay attention to the problem

Synthetic papers have different printing properties due to their different types. More use of single-color or single-color printing machine. Here are only general issues that should be noted when printing with a sheet-fed offset press.

1. Continued paper

The biggest difference between synthetic paper and natural fiber paper (abbreviated as plain paper) is that there is no problem with the direction of fiber alignment, and therefore there is no fiber direction of plain paper and cross-web, and the toughness is weak. Therefore, it is suitable for paper feeding from a central paper feeder, and adjustment of the air separator needs to be carried out with extreme caution. Even if various synthetic papers have been treated to some extent to prevent static electricity, static electricity is still more easily generated than plain paper. Therefore, it is preferable to install a corona discharge type static eliminator on the paper feed table.

2. Receiving paper

In general, the smoothness of the synthetic paper is extremely high, and the phenomenon of back rubbing is likely to occur, and the particles to be sprayed should be increased. However, the size of the particles should also be selected taking into account the conditions of post-press processing. In particular, when the surface of an ethylene film is processed, air bubbles with a core of powder occur. When synthetic paper is used, static electricity is removed by the automatic paper feeder, but it is recharged when it is detached from the blanket after the printing pressure is applied. This is because after the paper is delivered, the synthetic paper is attracted. For reasons of force, a static elimination device is also installed at the delivery site.

3. Ink

After the surface of the synthetic paper was processed, the ink receptivity was improved, but it was still inferior to coated paper. Therefore, it is preferable to use special inks for synthetic papers sold on the market. Because the substrate is "plastic", the oil absorption is also worse than that of plain paper. This is related to the fact that once the wetting fluid is absorbed, the transferability of the ink will be poor, so the wetting fluid should be reduced to the minimum during printing. From the perspective of poor ink absorption, the use of a strongly volatile or UV-drying ink can reduce ink transfer failure.

In addition, the surface of the synthetic paper is treated with inorganic substances. During the printing, particles that fall off will accumulate on the blanket, sometimes causing a phenomenon of ring-shaped white dots, which is different from the paper powder due to the adsorption of the blanket. Weak forces, prone to displacement, tend to disperse naturally, and are not easy to find, we must pay more attention.