Practical application of hot melt adhesive granules in sheet music books: A record of the page flipping and flattening transformation of a music textbook factory

The music score book has an almost strict requirement for the adhesive:After opening, it must be able to be spread flat on the piano stand and repeatedly folded for six months without falling off the page.This is completely different from ordinary books and magazines that only need to be firm. A printing factory specializing in music textbooks in Guangzhou encountered this hurdle in 2025, and finally solved it by replacing it with more flexible hot melt adhesive particles and adjusting the backing adhesive process. This article reviews the entire process.

How was the problem exposed

This printing factory originally used universal book and magazine adhesive granules to make 128g copperplate paper sheet music books, and the binding fastness was not a problem. However, customer feedback focused on two points: first, students from the music store reported that “the book is not pressed evenly and closes as soon as they release it”; The second issue is that after three to four months of use, cracks appear on the spine of the most frequently folded pages in the middle. The return rate once reached 4.7%, which puts a lot of pressure on a category with low single profit margins.

Diagnosis: Sufficient fastness, insufficient flexibility

After conducting three sets of controls, the technicians found that the softening point of the original adhesive particles was higher, and the adhesive layer was harder after cooling, forming a “hard beam” on the spine of the book. Music score books have a large format (mostly A4 vertical format) and thick paper. When flipping pages, the spine of the book bears much greater bending stress than ordinary novels. The hard rubber layer cannot withstand repeated bending and cracks at the weakest point. At the same time, the hard adhesive layer also means that the spine of the book has a strong rebound force, which is the physical reason for “uneven pressure”.

Three step transformation process

• Step 1: Change the flexible formula rubber particles.Choose book and magazine adhesive models with moderate softening point and better low-temperature flexibility, and the adhesive layer should maintain a certain degree of elasticity after cooling instead of a glassy state. The machine temperature has been lowered from 178 ℃ to 168 ℃, resulting in smoother glue lines.
• Step 2: Adjust the milling back and groove.The milling depth is increased from 1.2mm to 1.5mm, and the groove density is increased to allow the adhesive to penetrate deeper into the paper fibers, achieving fastness through “anchoring” rather than “thick adhesive layer”.
• Step 3: Optimize the side glue and compression.The width of the side glue has been reduced from 6mm to 4mm to avoid the side glue from “trapping” the book pages and affecting the spreading; The compression time has been extended from 1.2 seconds to 1.8 seconds to ensure sufficient penetration.

transformation outcome

It is worth mentioning that due to the use of penetration anchoring, the adhesive layer has become thinner, and the single adhesive consumption has been reduced by 8%. This indicates that ‘more glue=stronger’ is an intuitive trap.

Experience extraction

When making music score books, recipe books, fitness manuals, and other booklets that need to be spread out, when selecting glue, you shouldLow temperature flexibilityConsidering before the softening point, the process relies on milling back grooves to improve penetration, rather than thickening the adhesive layer. Guangzhou Sunlife Trading specializes in providing flexible backing adhesive models in the Sunlife hot melt adhesive book series, which can also be customized based on customer paper and format for sample verification.

Frequently Asked Questions

Q: Can’t music scores be directly bound with locking tape?
Answer: Yes, the lock thread adhesive has the best flatness, but the cost is significantly higher and the production capacity is lower. If the unit price space is limited, a wireless adhesive with flexible rubber particles and optimized milling back is a more cost-effective solution.

Q: Will switching to flexible rubber particles sacrifice durability?
Answer: No, the prerequisite is to adjust the milling back and pressing parameters accordingly. Flexible formulas rely on penetration anchoring to achieve fastness, and the measured folding life is actually longer.

Q: Is this plan suitable for sheet music with punched holes?
Answer: Loose leaf notebooks mainly rely on the force of the buckle, and the requirement for glue is transferred to the cover pasting process. The selection ideas are different, and it is recommended to make separate samples for confirmation.