How to use book hot melt adhesive correctly?

1. Hot glue for binding booksApplication of glue

（1）  Wireless Binding

Wireless binding is also known as glue binding or wireless glue binding. It does not use stitching or saddle pins to fix the pages, but instead uses hot melt adhesive to bond the cover and inner pages together to make a book block.

Usually, after organizing the pages by number, the spine of the book is polished flat with a milling cutter, grooves are pulled on the spine, and then the book stickers are firmly bonded with hot melt adhesive, followed by sticking the cover. Adhesive bound books come in either paperback or hardcover versions.

（2）  Thread glue bag

Thread glue binding is similar to the combination of “needle binding” and “wireless glue binding”. It is to first assemble and paste the inner pages of the book into a book, fix the back of the book with thread binding, and then use hot melt adhesive to stick the book on the cover. It is the best binding method for paperback books.

If the hot melt adhesive used for binding books is chosen properly and the binding method is correct, then our books can be used normally for many years.

2. How to correctly use hot melt adhesive to bond books?

（1）  Heating temperature

Book hot melt adhesive is very sensitive to temperature changes, and temperature directly affects its bonding performance. When reaching a certain temperature, the hot melt adhesive begins to soften, and below a certain temperature, the hot melt adhesive becomes brittle. Therefore, when choosing hot melt adhesive, the influence of temperature on its bonding performance must be considered.

Due to the need to heat hot melt adhesive before use, in order to ensure the quality of the bonded products, it is necessary to strictly control the temperature of the hot melt adhesive in the preheater and glue pot, especially in the glue pot.

The same type of hot melt adhesive, the higher the temperature, the lower the viscosity, and the easier it is to penetrate between pages, resulting in better binding quality. But it’s not necessarily the higher the temperature, the better. If the temperature is too high, the polymer of the main component of hot melt adhesive will undergo thermal depolymerization, thereby reducing the adhesive strength of the hot melt adhesive.

However, the temperature cannot be too low. If the temperature is too low, the fluidity of the hot melt adhesive will decrease, which means that the adhesion strength will decrease. For ordinary books, the heating temperature of hot melt adhesive is 140-170 ℃, and the preheating temperature of the preheater and glue pot is usually 15-20 ℃ lower than the working temperature of hot melt adhesive.

For books with thick book cores and good paper quality, the heating temperature of hot melt adhesive can reach 175-185 ℃. In addition, during the heating process, the hot melt adhesive needs to be continuously heated to maintain a constant temperature and avoid the impact of temperature changes on its performance.

（2）  Painting time

The curing speed of book hot melt adhesive is very fast, without the need for heating and drying. Hot melt adhesive can solidify after leaving the glue pot for 8-15 seconds. Therefore, it is necessary to control the coating time of hot melt adhesive.

Only by completing the painting work within this time frame can a good bonding effect be achieved. On the contrary, phenomena such as weak adhesion, non stick adhesion, and falling pages after pasting may occur.

（3）  Adhesive layer thickness

The amount of hot melt adhesive used during the coating process also directly affects the quality of wireless adhesive packaging. In general, people believe that the thicker the adhesive layer, the higher the adhesion strength between the paper sheets. This is incorrect.

In actual production, we found that when the thickness of the adhesive layer increases to a certain value, the bonding strength actually shows a downward trend. Therefore, if one blindly pursues an excessively thick adhesive layer, not only will it fail to achieve the desired bonding effect, but it will also waste hot melt adhesive, increase the thickness of books and magazines, and affect the reading effect.

Therefore, the thickness of the adhesive layer should be selected according to the thickness of the book, the type of printing paper, and the type of hot melt adhesive.