Frequently asked questions

FAQ's

1What temperature should I have the glue set to?
Always refer to the TDS, but typically hotmelt adhesives are applied between 150 – 170C. It is advisable to maintain the adhesive in the tank at the lower end of this range and should be at the higher temperature at the point of application, to ensure optimum performance.
2Why is the glue stringing, or creating a kind of web?
This is most likely because the glue is not hot enough at the point of application. If the adhesive temperature is low, it will start setting too early, and will string /web. Refer to the TDS and check that the temperature is as recommended.
3Are there different grades for different papers or substrates?
The short answer is Yes, and it is important to know when the substrates you are gluing have changed. (You might have changed your supplier of papers / board stocks and there could be a variance in the stock.) Some boards and papers have coatings / varnishes or toners that can have different chemical compositions which can affect the performance of the glue itself.
4Why is the adhesive not working?
These causes are most likely due to wrong machine settings. Check the temperature settings as it is common for the thermostats in the glue tanks to lose their calibration and therefore the displayed temperatures may not always be the true temperature of the adhesive resulting in poor adhesion.
Has the printed stock or paper supplier made changes to their usual substrates? Take into account all the variables.
5Does a cold environment / hot environment affect the adhesive bond?
Adhesives are synthetic polymers and have physical parameters that will alter at the varying temperatures.
In the case of emulsions (water- based polymers) they should not be exposed to cold temperatures below 5C as there is a risk of frost which can shock the polymer out of the system
Hotmelt adhesives by their very nature, soften at high temperatures and so bonds made with HMA resins may “creep” under pressure resulting in cohesion failure
We can offer a range of adhesives that are better suited for such conditions; however, it is advised that these grades are tested for acceptance before any commercial production is assigned.
6Will more glue help if the glue flaps pop open?
No. Increasing the quantity of adhesive on a seam / glue flap will require more drying time. As long as the adhesive remains wet, the bonds will not form and the flaps will “pop” open.
This can be mitigated by using a higher-tack adhesive and increasing the compression time.
It is also important to make sure that the pressure belts are exerting the pressure on the glue lines directly to allow maximum wetting of the substrate.
Some substrates are laminated / coated and this makes the surface non-porous. It is important to ensure that this is avoided as it will affect the bond.
7Is the glue approved for indirect food contact?
Yes, all of our adhesives are FDA approved for indirect food contact.
8Is Metallocene hotmelt better than a standard EVA hotmelt?
Metallocene hotmelts have better thermal stability and great cleaning properties and therefore will not “char” as readily, thus keeping the application equipment clean.
However, if you have difficult substrates to bond, then the older technology is still the best.

Understanding water-based film to print lamination adhesives


TYPICAL MACHINERY: Billhofer, Paperplast and Autobond
Product Code: KR1225

1How fast can I run the machines?
KR1225 is approved for speeds of more than 50M/min but the running speeds chosen depend very much on the job being laminated. (Most print finishers will run at a max of 30M / min).
2What quantity of adhesive can I apply?
The amount of adhesive applied depends on many factors like speed, the type of print, as well as type of film being used.

As a guide you could use the below test data

  • Matt film: 8-12 GSM dry
  • Gloss film: 6-9 GSM dry
  • Allow for higher GSM when laminating dark prints (blues, reds and blacks)
3Why are there streaks on the print after lamination?
If too much adhesive is applied, it will remain wet after lamination and this will show as “streaks” in the film. You need to slow the machine so the laminate has longer time in the drying chambers OR reduce the adhesive quantity being applied.
4What is silvering?
If the quantity of adhesive applied is not enough then after lamination, the print areas that do not have enough adhesive will show up as “silvering”. (More common on darker print backgrounds like Black / navy and reflex blue).

To avoid silvering, increase the quantity of adhesive and reduce the speed of the machine to allow optimum drying time. Ensure that you are using a high-solid acrylic adhesive like the KR1225.
5What are “fish eyes”?
Old film inventory may have lost its corona treatment (check the dyne value) stopping the adhesive from wetting the surface of the film evenly thus causing reticulations or “fish eyes”.

Avoid using oil / terpene-based cleaners as these are not water-based and can also cause reticulations.
6What are dry-lines?
Dry lines appear on the film before lamination due to the presence of a dried particle on the doctor blade. General cleaning is recommended.

It could also indicate that the filters on the machines and pumps need to be replaced.
7Why is the laminate lifting?
After lamination, the laminate may be required to be further processed (creased) and at that point the film should not lift under pressure.

If it does lift then this is often called “milking” and can happen if the adhesive had not fully cured. (Typically, 8-12 hrs should be allowed for before laminates are further processed)

The lifting can also occur if the ink used during printing has not fully cured or there may be an incompatible coating that is not allowing the adhesive to “key” properly.