How can wireless adhesive books be spread out without falling apart? The selection of hot melt adhesive particles is key

Direct answer: To “spread evenly without falling apart”, rely on flexible rubber particles

The key to choosing a wireless adhesive book that can be spread out without losing pages is to choose a flexible type that has good extensibility and does not become brittle at low temperaturesHot melt adhesive granulesAdd sufficient milling depth and adhesive amount. Many people think that the harder and more sticky it is, the stronger it is. In fact, a hard adhesive layer will form a hard shell on the spine of the book. When the book is flattened, the stress is concentrated at the folds, making it easier for the spine to crack and the pages to fall off.

Four real reasons for falling apart

• The adhesive layer is too rigid: when the spine of the book is compressed, it cannot bend along with it, and the adhesive film is directly brittle and cracked;
• Insufficient penetration: The glue only sticks to the surface of the paper edge and does not “bite” into the inside of the paper fibers;
• Milling back too shallow or too deep: If it is too shallow, the adhesive area is not enough, and if it is too deep, it will damage the strength of the paper;
• The direction of the threads is incorrect: When the paper threads are perpendicular to the spine, there is a high resistance to turning pages, and even if the glue is good, it will be difficult.

Judging flexibility by three parameters

Two more steps to coordinate on the production line

One is to control the milling depth at 0.8-1.2mm, so that enough fuzz is formed on the paper edge; The second is to adjust the amount of glue according to the format, usually 0.5-0.7g/book for 16 format brochures, and press and hold for 2-3 seconds. The flat adhesive granules for Sunlife hot melt adhesive are formulated according to the direction of high elongation. Guangzhou Sunlife Trading can send samples and test the adhesive according to your paper sample and format, and conduct a test first before measuring the quantity.

Don’t ignore acceptance and storage

Flexible granules are more sensitive to moisture, and micro bubbles are easily generated inside the adhesive layer after moisture. When bent, they crack from the bubbles. Before arrival, check whether the particles are uniform and free of clumps. After opening, be sure to tie the inner bag tightly and place it in a cool place. It is recommended to use desiccants during the southern rainy season. In addition, if the inner pages of the same book are mixed with copperplate paper and writing paper, the adhesive should be selected and the amount of adhesive should be determined according to the most difficult to stick paper, otherwise the thin paper should be firm and the coated paper should be opened first.

Frequently Asked Questions

Q1: Do I have to use PUR glue for flat bread?
not always. PUR has good flexibility, but the equipment and cost threshold are high; Generally, high elongation EVA flexible grades are sufficient for picture books and notebooks.

Q2: How to quickly test if it can be spread evenly?
Spread the finished product flat and press for 30 seconds, repeat 20 times, check for cracks on the spine and looseness on the inner pages.

Q3: Can increasing the amount of glue solve the problem of loose racks?
No. Excessive glue will only overflow and dirty the pages. If the flexibility is not enough, whether to crack or not, it is necessary to change the glue type first.