There are many binding methods available today, such as PUR (Polyurethane Reactive-Polyurethane Reaction), EVA (ethylene vinyl acetate-ethylene acetate) hot melt, and PVA (Polyvinyl Acetate Acetate) cooling emulsions. There are also various kinds of sewing and binding. The PUR appeared around 1989 and was first tested and applied on a manual bookbinding system in North America. According to National Adhesives, which introduced PUR to the US book binding market, the binding process was mainly made up of quality books, annual reports, Used in catalogs and magazine publishing.
Why PUR?
Since its birth, PUR's growth rate has been relatively fast. In 1995, there were only 28 users in North America. By the end of 2002, there were more than 50 users. There are many reasons why PUR replaces commonly used hot melts, the most important of which is its superior adhesiveness and the ability of the PUR process to fully unfold books.
Adhesive
PUR is very effective for the treatment of surface film, UV film or paper products, which is mainly determined by the polar nature of the polyurethane molecules, it can be well combined with the surface coating layer, to achieve high-quality adhesive Effect.
Variations in the grammage of the paper, the use of paints and inks are almost unaffected by the effect of the PUR adhesive. The new PUR product can firmly bind all types of coated paper together. According to reports, the pull force of PUR paper is 40%-60% higher than that of ordinary adhesives.
For conventional adhesives, if the ink accidentally flows to the bookbinding line, it will affect the quality of the binding, resulting in binding failures. For the PUR process, these phenomena will not have any effect on the binding.
Super book balance performance
The recommended thickness of the PUR coating is 0.01 inches, which is much softer than the standard EVA hot melt. This property allows the PUR-bound book to spread smoothly without hand pressure. For some types of books, such as instruction manuals, manuals, etc., it is very important to have good balance.
Other benefits
The other benefits of PUR binding are:
1. Cold and heat resistance
Books bound by PUR are not affected by temperature and withstand temperatures ranging from 200F to -40F. These properties are very important for the existence of books in different temperature environments. According to statistics, after the switch to PUR glue, the customer's complaints and complaints about the stickiness of adhesives are reduced a lot and are almost gone.
2. Books do not wrinkle
The use of standard hot melt to bind the cross-hatch paper tends to wrinkle at the book's gutter, and the lower PUR blending temperature does not evaporate the water inside the paper at the spine and, therefore, does not tend to wrinkle. phenomenon. In addition, when the PUR is cured, it has a certain degree of ductility and does not affect the fiber direction of the paper. Therefore, the paper does not wrinkle.
3. No gap will occur
Since the coating thickness of PUR is only half that of the standard hot melt coating, it is unlikely that thicker material will accumulate at the knife, and no unevenness will occur during cutting.
4. Square spine
Since only a small amount of PUR is needed to complete the binding, no excess glue will be squeezed out when the book cover is installed, so that the shape of the spine will remain good.
5. Anti-solvent erosion
According to experts, PUR is currently the only binding material that resists solvent and oil attack. Cured PUR material can penetrate oils and solvents used in printing, such as methyl ethyl ketone (MEK) and alcohol. These chemical reagents There is no effect on the PUR film. With traditional glue binding, some chemicals will make the hot melt film slowly soften or even dissolve, which greatly reduces the effect of the binding.
Hardcover Advantage:
Binding companies engaged in hardcover books or multi-volume book binding can appreciate the benefits of PUR over normal wireless binding:
1. Save cost vs. Smythe lock line
For many years, the industry usually used Smythe locks, sizing, and rounding processes to produce hard-shelled hardback books, which were glued with a soft liquid glue before rounding. After investigating the European market, it was found that the grinding of the spine with good adhesion and then the adhesion with PUR glue can save at least 30%-40% of the cost.
2. Roundness retention
Many hardcover books are rounded and ridged to add beauty to the book and the strength of the final product. Using PUR glue to glue the spine gives a very good roundness. Next, you can get good results by rounding the book and raising the spine. When the PUR is cured, the book can be kept in a circular shape, and the arc's staying power will be maintained to the utmost. With the use of hot melt adhesives, the spine's roundness can easily be lost.
3. Application equipment
In the application of PUR, special attention should be paid to avoid premature and prolonged contact with air and cross-linking in order to avoid curing. The glue pan and the closed extrusion system are the necessary equipment. The old-fashioned binding equipment can be transitioned to the high-end PUR binding with the necessary modifications.
