The quality of back work
The quality of milling and roughening the back of the book is the main factor that affects the fastness of wireless binding. The characteristic of the quality of the surface processing of the book back is the macro and micro geometric shapes of the paper surface of the book back, which can be expressed by the average arithmetic value of the macroscopic non-slip of the paper end. In the process of milling and roughening the back of the book, the fibers on the edge of the paper are loosened and a rough surface is formed, and the glue penetrates along the fibers to the surface of the paper and adheres to each other. The back of the book is not roughened, the milling cut is smooth, and the bonding surface of the paper and the glue is small, so that the glue can not be infiltrated and adhered to the paper. The back of the book is roughened to form a rough surface. Similarly, the glue is not easy to soak in the paper, because paper wool and air accumulate on the surface of the book back, which prevents the glue from contacting the paper. Milling the crease of the back of the book with a blunt knife to obtain a rough surface of the back of the book also affects the fastness of wireless binding.
Hot melt temperature
Different types of hot-melt adhesives have different bonding properties. For the same hot-melt adhesive, as the temperature increases, the lower the viscosity, the better the wettability of the glue between the back of the book and the pages, the wireless adhesive The better the fastness. When the temperature is too high, the polymer as the main component of the hot melt adhesive may undergo thermal depolymerization, thereby reducing the adhesion of the hot melt adhesive. If the temperature is too low, the fluidity of the glue solution is poor, affecting the adhesion fastness of the glue. At present, the hot melt adhesives commonly used in printing plants have good viscosity and wettability at 170 ℃ ~ 185 ℃, so they need to be continuously heated and maintained at a constant temperature during use.
Thickness of adhesive layer
As the thickness of the hot melt adhesive layer increases, the adhesion fastness increases. When the thickness of the adhesive layer increases to a certain value, the adhesion fastness begins to decrease. This shows that using an excessively thick hot-melt adhesive layer not only wastes glue, but also reduces the adhesion fastness, and also destroys the overall structure of the book.
The thickness of the hot melt adhesive should be determined according to the thickness of the publication, the type of printing and cover paper, the type and quality of the hot melt adhesive. Generally speaking, under the condition that the latter two conditions are basically the same, the fastness of wireless perfect binding depends on the thickness of the book block. Regardless of whether the fiber direction of the paper and the back of the book block are parallel or not, the thin book block has the best adhesion fastness, the medium-thick book block adhesion is second, and the thickest book block has poor adhesion fastness.
The results of this study indicate that for book blocks of different thicknesses, the appropriate thickness of the adhesive layer should be selected. For example, for a book printed with letterpress paper and having a thickness of 10 to 12 mm, the thickness of the hot-melt adhesive layer is 0.4 mm. For publications with a thickness of 20 mm and thicker, the thickness of the hot-melt adhesive must reach 0.8 to 1.0 mm. The degree of compression of the cover and book block. The cover should be firmly attached to the back of the book and various parts on both sides of the book, without wrinkles, and the back of the book should be neatly rectangular.
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