Does paper powdering cause the hot melt adhesive to not stick firmly? Reasons and solutions for the weak adhesion of copperplate paper/coated paper

#Does paper powdering cause the hot melt adhesive to not stick firmly? Reasons and solutions for the weak adhesion of copperplate paper/coated paper

Books, brochures, and covers are often made of copperplate paper and coated paper, which have a beautiful surface but often have strange binding issues: the glue coating “hangs” on the surface, the book pages fall off as soon as they are flipped, or the glue just leaves the machine and opens after two days. Many masters’ first reaction is’ glue doesn’t work ‘, but in fact, the root often lies inPowder loss on paper and coating affecting penetrationUsing Sunlife’s real selection logic, explain this matter clearly below.

1、 First of all, the conclusion is that not sticking firmly is not necessarily a problem with the glue, it may be due to the glue not being able to feed properly

Hot melt adhesive spine relies on the infiltration of paper fibers and the formation of mechanical interlocking after cooling. Copperplate paper and coated paper have a layer of coating (calcium carbonate, porcelain clay, etc.) on their surface. If this layerPowdering and sheddingOr if the coating is too dense and not breathable, the glue can only stay on the surface, forming a “false adhesion” – it looks like it’s stuck, but it doesn’t actually bite, and it opens after flipping it a few times or being compressed.

For this type of problem, switching to more expensive glue often treats the symptoms rather than the root cause, and we need to address it fromPaper state+adhesive penetration designBuy from both ends.

2、 Why does paper powder fall off and cause weak adhesion

• Powder layer isolationThe floating powder on the paper surface forms a layer of “isolation film” on the spine of the book, and the glue cannot penetrate into the fibers;
• Dense coatingPart of the coated paper has a tight coating with few pores, making it difficult for the adhesive to infiltrate;
• Insufficient back milling and hair pullingThe spine of the book is not brushed or brushed lightly, the fibers are not exposed, and the glue has no “grip”;
• Environmental humidityReturning to the southern sky/high humidity makes the powder layer looser, easier to fall off, and the adhesion worse.

As mentioned in Sunlife training,Suggested workshop environment: 15-26 ℃, humidity of about 50%Abnormal temperature and humidity can magnify paper problems.

3、 How to handle it (on-site can be landed)

1. First, confirm if there is any powder loss

Scratch the spine of the book with your nails to see if there is any white powder peeling off; Or check if the adhesive layer “floats” on the surface and falls off as soon as it is peeled off. If you’re losing powder, don’t rush to change the glue.

2. Choose the right adhesive for copperplate paper

Copperplate paper and coated paper should use specialized adhesive designed for permeation. Sunlife corresponds to 396(with fillers to enhance bite)/ 397Two copperplate paper backing adhesives with no fillers and smooth coating compatibility have been formulated to address the issue of “difficult coating penetration”.

3. Make the milling back sufficiently hairy

Mill the spine of the book and pull the hair until the fibers are exposed, leaving a “grip” for the glue. Shallow pulling is the high-frequency reason for this type of glue opening.

4. Align temperature and adhesive amount

The melt adhesive should be kept within the process window of 160-180 ℃ (temperature is not sufficient for poor infiltration), and the amount of adhesive should be sufficient according to the thickness of the book without overflowing; Sunlife training emphasizes 90% of after-sales service is due to equipment temperature control failureFirst, calibrate the actual temperature of the glue pot with a thermometer.

5. Control environmental humidity

Pay attention to dehumidification in the workshop during high humidity seasons to avoid loosening of the powder layer and slow curing of the adhesive.

Frequently Asked Questions

Q: Copperplate picture books always have adhesive peeling, should we switch to stronger adhesive?

A: First, check for powder loss on the paper surface and burrs on the milling back. If powdering causes the adhesive to stick to the surface, the effect of changing the adhesive will be limited; Only by using special adhesive for copperplate paper such as 396/397, doing sufficient roughening, and calibrating the temperature, can the problem be solved.

Q: Will regular adhesive paper lose powder?

A: Yes, but coated paper is more typical. Double adhesive paper and adhesive packaging paper are relatively easy to penetrate, corresponding to 292/296/295; If you really encounter powder loss, first check the pulling and temperature.

Copperplate/coated paper may not stick firmly, so don’t rush to blame the glue – it’s mostly due to paper powdering and glue not being able to feed. Follow the four steps of “checking off powder → selecting 396/397 copperplate paper special adhesive → making sufficient hair → calibrating temperature”, which is much more stable than blindly changing the adhesive. If you can’t get it on time, please tell Sunlife the sample book and match it with the paper type and process card.

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