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As offset presses become more and more common, and the printing speed is becoming higher and higher, the surface strength of printing paper has become a more important performance index than printability, and it has become the most intense nature of certain paper types. .
The surface strength of paper refers to the degree of firm binding of the fibers, fillers, pigments, etc. on the surface of the paper to the bonding of the paper, that is, the strength of the bonding of the materials of the straight paper surface to each other.
When the surface strength of the paper is certain, the printing and sticking effect will be enhanced during printing, and hair loss and powder dropping will occur on the paper surface. Therefore, the surface strength of the paper is generally represented by its ability to resist hair loss and powder loss.
In the printing, the surface fibers, fillers, pigments, etc. are less likely to be pulled out by the ink and the surface strength of the paper is increased.
The water resistance of paper can cause paper to undergo varying degrees of surface strength change during offset printing. The so-called water resistance refers to the ability of the paper to maintain its original strength after being subjected to the action of infiltrating water, and expresses the stability of the paper after the performance of the water.
Since offset printing is performed under the condition that the infiltrating water is involved, it is necessary to consider the change in the surface strength of the paper when it is infiltrated with water.
In both papers, the surface strength may be the same before the surface is affected by water, but when it is soaked by the same amount of water, the surface strength shows a difference, which indicates that the water resistance of the two papers is different. Of course, after the general paper has been immersed in water, its surface strength will decrease, but the degree of decline will be different.
Therefore, when analyzing the surface strength of paper, the strength of water resistance must be taken into consideration. Foreign countries have special coated paper used for letterpress printing. This kind of printing is easy to get rid of in the offset printing. The reason for this is that the adhesive used in the paper is water-soluble and therefore has poor water resistance.
In the printing process, problems concerning the surface strength of the paper often occur. That is to say, the paper's anti-linting ability and powder dropping ability have a prominent influence on printing, and even restrict the printing efficiency and printing quality to a great extent.
On the offset printing paper, the fibers on the surface of the paper must be combined with each other. The filler particles must also be bonded with the viscose, and the water resistance must also be better. Otherwise, the fine fibers and the filler particles will be lost. Left white spots on prints, even large white spots appear in heavy ink images.
Falling filler particles and fine fibers can also clog the text and patterns on the overflowing paper. The graphics are becoming less and less clear. Even for coated printing paper, if the filler particles do not have sufficient bond strength with the fibers, it will also happen. The above phenomenon.
Practice has proved that the failure of paper in the printing process is a problem that is currently prominent in China's printing paper, especially offset printing books and papers.
In the offset printing rotary presses where the printing speed has been increasing, the surface strength and water resistance of the used papers have been further improved in multicolor printing using high-viscosity inks without high quality.
Dealing with paper surface problems will not lose face.