Can hot melt adhesive particles be recycled and reused? Five Common Misconceptions Don’t Step on Again

Direct answer:Hot melt adhesive particles belong to thermoplastic materials and can theoretically be melted repeatedly, but in most cases, “recycling and reuse” on the production site is not cost-effective or safe.There is only one situation that can be recycled – clean residue that has never been used on the machine and has not been contaminated; Residual glue that has been heated for a long time in the melt glue pot or mixed with paper scraps and dust will significantly deteriorate in performance after remelting, and the risk is far greater than the material cost saved.

Misconception 1: Adhesive is thermoplastic, it doesn’t matter how many times it melts

Thermoplasticity only indicates that it can repeatedly soften, and does not mean that the molecular structure is not affected. Every high-temperature melting will cause oxidation of some of the thickening resin and breakage of some polymer chains, resulting in yellowing of color, decrease in viscosity, and attenuation of initial adhesion. In actual testing, after the same batch of adhesive is repeatedly melted three times at 180 ℃, the viscosity often decreases by more than 15%, and the adhesive fastness decreases accordingly.

Misconception 2: Residual glue from the bottom of the pot can still be used after being scraped off

The residue at the bottom of the pot is the least recyclable part. It has undergone the longest period of heating and is usually carbonized. When it is removed and remelted, it will bring in black slag, directly causing nozzle blockage, black spots on the glue line, and even contaminating the entire batch of book cores. The correct approach is to regularly clean the pot with specialized cleaning agents and dispose of residual glue as solid waste.

Misconception 3: It’s okay to mix the cut edges back together

The scraps cut from the adhesive book carry paper fibers, ink, and dust. After remelting, these impurities will not disappear, but will only become suspended solids in the glue pot. Light cases can block the nozzle, while heavy cases can create stress concentration points in the adhesive layer, causing the spine to crack prematurely when folded.

Misconception 4: Residual glue from different batches can be combined for use

The softening point of different batches of the same model is allowed to have a normal fluctuation of ± 2-3 ℃. It is not a problem to use it alone, but mixing it together will make the melting curve unpredictable and the adjustment parameters difficult to stabilize. If it is indeed necessary to merge, it is necessary to conduct sample verification on the same device first.

Misconception 5: Recycling can save a lot of money

Calculating an account is more intuitive:

For a glue binding line that produces tens of thousands of copies per day, one shutdown and repair caused by black residue blockage is enough to offset half a year of “recycling revenue”.

So under what circumstances can it be recycled

• Unopened bags of leftover materials that are within their shelf life and stored under normal conditions can be used directly.
• Rubber particles that have just been unpacked and have not been loaded onto the machine, are not affected by moisture or pollution – sealed and labeled with batch numbers, and should be used first in the next shift.
• During the trial run, if the glue is heated for a short period of time, without impurities mixed in, and the color remains unchanged, a small amount of new glue can be added (recommended not to exceed 10%), and the first piece confirmation should be done.

The more fundamental way to save money isReduce the generation of surplus materialsAdd glue in small batches according to the shift usage, control the amount of glue in the pot to the lowest before leaving work, and use up one bag before opening a new one. When Guangzhou Sunlife Trading calculates the usage for customers, they usually provide recommendations for the glue adding rhythm. Sunlife’s hot melt adhesive series also offer various packaging specifications for easy access according to needs.

Frequently Asked Questions

Q: Which is better, overnight insulation or reheating of the glue pot the next day?
Answer: Re heating is better. Long term insulation is equivalent to continuous thermal aging, and overnight insulation glue often turns yellow and viscosity decreases the next day. Unless the device has a low-temperature standby function, it is recommended to turn off the power after work.

Q: How to do first piece confirmation for recycling glue mixed with new glue?
Answer: Observe whether the glue line is continuous and whether the color is abnormal, then conduct a hand tear fiber damage test to confirm that the fiber damage rate is consistent with pure new glue before continuing production.