First, the binding form of books
Under certain conditions, a substance that can bind together the same kind or different kinds of solid materials through the interface is called an adhesive, which is a kind of adhesive material.
The method of joining the surfaces of two solid materials through the adhesive force of the adhesive is called bonding. In book binding, one of the most important ways to link individual pages into books and books is to bond. Therefore, adhesive materials are important materials for book binding production.
In book binding, the bonding forms are: end face bonding and planar bonding. The lining, inserts, forms, etc. are connected to the signatures, the lining strips, the cover of the package, the backs of the hardcover book blocks, the production of the book shells, and the upper case are all bonded together. Wireless glue binding and hot-melt hot-stitching are end face bonding. Plane bonding is overlap and the contact area is relatively large, so it is relatively strong. The adhesive bonding of the end face is achieved by the adhesive penetrating the pages of the book so that the end faces of the paper are bonded to each other. According to the penetration depth of the adhesive between the paper and the thickness of the formed film, the bonding rate is also the same wood.
Second, the binding adhesive requirements
In bookbinding, the objects to be bonded are mainly fiber materials (paper, cardboard, cloth, etc.); if the books are filmed, the bonded object is the bond between the fiber material and part of the plastic film layer. Bonding fastness directly affects the bookbinding quality. It not only depends on the structure and properties of the surface of the adhesive and the adhered object, but also has a close relationship with the operating conditions of the bonding process.
Therefore, in addition to the properties of the surface of the adhered object, the selection of the adhesive should be based on the binding process and the requirements during the use process.
1. Binding process requirements for adhesives.
(1) Liquidity. Adhesives for books and bookbinding must have good fluidity so that the glue can fill the pores on the surface of the adhered object. When the adhesive is bonded, it can achieve full and real contact with the uneven surface of the adhered object.
(2) Wettability. In order to obtain the ideal bonding effect, the adhesive should be well coated on the surface of the adhered object and should have the largest possible contact area with the surface of the adhered object. That is to say, only when the adhesive sufficiently wets the surface of the adhered object and then loses fluidity and produces strong cohesive force, an intact adhesive effect can be produced. Therefore, wetting is a prerequisite for adhesion. Only when the surface tension of the liquid is less than or equal to the surface tension of the solid is the condition for the complete wetting of the liquid on the solid surface. Therefore, the surface tension of the adhesive should be as small as possible. In this case, the contact angle of the liquid adhesive to the surface of the adhered object is less than 90, so that the surface of the adhered object can be wetted.
(3) Viscosity. In order to obtain a good bonding effect, in addition to the adhesive can be fully wetted and penetrated on the surface of the adherend, it must also have a bond strength. The bond strength is determined by the cohesion of the adhesive itself and the adhesion between the adhesive and the adherend. The viscosity of the adhesive, in addition to directly affecting the wetting and penetration speed of the adhesive on the surface of the adhered object, is also a major factor affecting the bond strength.
High-viscosity adhesives have high solids content, low moisture content, high cohesion, and high bond strength. However, the adhesive has small fluidity and is not easy to infiltrate. Therefore, it is mostly used for bonding small objects such as sticky single pages, illustrations, and package covers.
The adhesive with low viscosity has good fluidity, and it easily fills all the micropores on the surface of the adhered object to increase the surface area of ​​the adhesive, but its solid content is small, the cohesion is small, and the adhesive strength is also small. It is absorbed by the bonded object and the remaining adhesive material is insufficient to form a strong adhesive film on the bonded surface.
In the binding production, mostly water-soluble adhesives are used, and as the moisture evaporates, the viscosity of the adhesives also increases.
For hot melt adhesives, as the temperature changes, it also leads to a change in the viscosity of the adhesive, which greatly affects the adhesive properties of the adhesive. In order to ensure the fastness of the bonding, the viscosity must be controlled when preparing and using the adhesive according to the type and performance of the adhered object and the adhesive.
(4) Coating time and setting time. The binding adhesive should have a certain coating time and setting time. The coating time limit refers to the time that the adhesive does not lose its viscosity after it is applied to the surface of the adhered object. This duration should be the time necessary to complete a binding job. This is the only way to ensure that the two bonded objects stick together at the desired location before the adhesive cures.
(5) The properties of the adhesive material must be stable during adhesion of the adhered object.
2. The use of adhesives
(1) The aging period of the adhesive should be higher than that of the designed publication to ensure the normal use of the publication.
(2) The adhesive should be neutral or slightly acidic in order not to damage the cellulose-containing adherends, discolor it, or fade the printed graphic.
(3) The adhesive should be colorless and transparent.
(4) Adhesive strength should have strong adhesive force. To stick the adhered object, the strength of the adhesive layer should be higher than or equal to the strength of the adhered object.
(5) The adhesive layer should have a certain degree of flexibility to ensure that the film is not destroyed during the further processing of semi-finished products and during the reading, preservation and transportation of books.
(6) Adhesives should be odorless, non-toxic, non-mildew, not insects, not afraid of rat bites, non-flammable and inexpensive.
The above is the common requirement for the adhesive. When a specific process is completed, the adhesive with the right performance should be selected according to the characteristics of the process. For example: 1 Adhesive ring liners, inserts, tables and other leaflets, due to the small area of ​​the bond, but also bond firmly, so need a large viscosity adhesive. 2 Adhesive glue used on the back of the book should ensure that the folds at the edges of the book are firmly bonded, so that the adhesive film at the joint has a certain degree of flexibility, and can keep the book back from arching. Therefore, depending on the type of printing paper, choose an adhesive with suitable properties. 3 When using wireless glue binding, the adhesive should have the proper viscosity. When the viscosity of the wave liquid is too high, the fluidity thereof becomes poor, the permeation performance is not good, and the glue liquid is not easy to fill the pores of the bonded surface, and the binding of the book sheet is not firm; when the viscosity of the glue liquid is too low, when the glue is low Again, a sufficiently thick adhesive film layer cannot be obtained. 4 in the cover and the end of the book, because the brush and the package cover or the bookcase is not a process, in order to catch up with the beat of the linkage production line, but also to facilitate correction, can make the cover material or relative slide between the bookcase and the back of the book , should use a longer solidification time, sticky adhesive.