Comprehensive analysis of the application of PUR glue in book printing

The relationship between PUR adhesive and hot melt adhesive

Hot-melt adhesives are a large category, and PUR is just one of them. Most hot-melt adhesives are heated and can be reheated after bonding. It is reversible, and PUR is a moisture-reactive hot-melt adhesive. After heating, it will react with the moisture in the air after bonding, and it will be irreversible after the reaction (that is, it will not melt when heated). Therefore, PUR is more resistant to high and low temperatures.

Application in Book Binding

Compared with standard EVA hot-melt adhesive, PUR adhesive has a smaller amount of spine adhesive. Although the amount of adhesive used is less, the strength is not reduced but increased. PUR glue is much softer than standard EVA hot melt glue, so the book is very flat when opened, and it can be spread out well without pressing with hands when reading. The flatness of the book improves the reading comfort of the reader. Books bound with PUR glue have a strong adaptability to the environment, and are particularly resistant to high and low temperatures. In the case of ideal page material, PUR glue binding will not have a problem at a temperature of -40 degrees to 120 degrees. This is precisely its excellent characteristics for adapting to hot and cold environments, which is far better than other hot melt adhesives. Worry about the influence of book binding temperature on its quality. When using ordinary hot-melt adhesive to bind book blocks of horizontally threaded paper and irregularly textured special paper, a lot of wrinkles will be generated in the grooves. The low bonding temperature of PUR glue (the normal operating temperature is 120 degrees) will not evaporate the water inside the paper at the spine. At the same time, the PUR glue layer has a certain ductility during the drying process, so that the paper fibers can be restored. As long as the roughing and slotting methods of PUR binding books and journals are correct and the operation is proper, there will be no opening of glue and pages, and the appearance will be neat after binding into books. Also, because the amount of PUR glue used in binding is less than that of other glues, very little adhesive is squeezed and oozed out when encapsulating the top and side glues and the top cover. Uneven phenomena or gaps appear to keep the spine form good. The PUR adhesive layer is firmly formed and has strong solvent resistance. Until now, PUR adhesive is the only binding material that is both solvent-resistant and grease-resistant.

The EVA hot-melt adhesives currently used are easily affected by the petroleum-based solvents in the ink components, making them slowly soften or even dissolve. As the EVA hot-melt adhesive softens, the strength decreases, and serious quality consequences such as the shedding of pages will occur. It can be seen that PUR glue is not affected by the solvent and maintains the original strength of the glue, which greatly promotes the improvement of book binding quality.

For many years, the book blocks of the round spine hardcover books have been fixed with a lock thread. Before the round is rounded, a layer of adhesive with good toughness must be coated on the book block with the lock thread. It is a good choice to use PUR hot-melt adhesive for round-back hardback pulp back. It has unique forming flexibility and high adhesion, which is more suitable for binding hardcover books and readers' flat reading requirements. According to the calculation of this binding method, it can save about 20% -30% of the cost, so PUR glue binding is lower in cost and better in quality than the wire binding. The new generation of PUR hot-melt adhesive can be linked with the round, brush PUR adhesive on the book block, and then round and ridge, can get a more refined round spine, because the PUR adhesive layer and the book block are in a round shape It is dry in the state, so the durability of the round book back can be maximized. While ordinary hot-melt adhesives are used to bind book blocks, they are usually brushed first and then rounded, so the durability of the round is far from the binding effect of PUR adhesive bonding.

The cost

PUR hot melt adhesive has so many benefits, but it has not been widely used, and its main problem is cost. Although the price of PUR adhesive is about three times that of ordinary hot-melt adhesives, the quantity used is only half of that of ordinary hot-melt adhesives. This number is quite important when considering the cost of the entire book. For example, a 16k book, about 2.5cm thick, costs about 0.1 yuan for ordinary hot-melt adhesives, while using PUR glue to glue the same book costs about 0.16 yuan. The use of PUR glue also has a cost of equipment modification. The modification of binding equipment will probably cost 300,000 to 400,000 yuan, while the application system will cost an additional 200,000 to 300,000 yuan. It is these costs that hinder the promotion of PUR glue.