In the 21 century, we can’t live without the application of flexible packaging. From the snacks and bread on the shelves of the convenience store to the fresh food in the supermarket (as the image below), this food packaging is called flexible packaging. Because food packaging appears everywhere in our daily life, it highlights the importance of eco-friendly adhesive for flexible packaging. In the previous articles (see the more article below), we already mentioned the overall introduction of adhesive for flexible packaging and high-temperature retort pouch. Now we’re going to introduce the adhesive for solvent-free flexible packaging, explaining the advantages of eco-friendly adhesive and how to use this adhesive to laminate flexible packaging.

【More article：What do you know about the food packaging of chips？】
【More article：High-Temperature Retort Pouch-Heat Tolerance Up to 135℃】
 

The advantages of adhesive for solvent-free flexible packaging

1. It doesn’t cause environmental pollution
Because the adhesive itself is a solvent-free adhesive, there is no solvent volatilized during the process, so it wouldn’t pollute the environment.

2. Lower the energy usage.
During the making process, there is no need for drying equipment to dry the solvent.

3. Erase the erosion of the solvent to printing ink.
Generally, the ink would be affected by the solvent and have a harmful effect. The solvent-free adhesive wouldn’t affect the function of ink.

4. Reduce the cost.
The amount of glue of adhesive for solvent-free flexible packaging is less than the solvent adhesive to reduce the cost.

5. Having a stable finished product.
To allow the finished product to steady, it would erase the effect of high temperature and solvent.

6. Apply small space to process.
The equipment is simple, and the space it used is much smaller than solvent adhesive.

The solvent-free laminating craft process

There are six steps of the solvent-free laminating craft process, which are:
1. Unreeling
Under a certain tension, expend the substrates to laminate and gum. Substrates can be two-level, which are main substrate and vice substrate, and the relevant unreeling processes are main unreeling and vice unreeling.

2. Gumming
At a fixed temperature, mix the adhesive in a certain ratio, and transfer it to the laminating machine where it stores glue.

3. Coating
On the basis of the laminating machine structure and product requirement, we evenly coat the adhesive on the substrate.

4. Laminating
On the certain and even pressure, we laminate the main substrate with the vice substrate.

5. Reeling
Reeling the laminating film with a certain tension and reeling pressure.

6. Curing
Put the laminating product in the environment at a certain temperature, and let the adhesive reach expect laminating fastness. Curing is the most important process in the solvent-free laminating craft process; it usually takes a longer time to finish.

 

The solvent-free laminating craft process common problems and solutions

During the process, there are two common problems, which are white dots and phenomenon and bubble phenomenon. The contents below are the common problems and corresponding solutions.

1. White dots
When the compound process ends, you can see different sizes of white dots on the products; this is called the white dots phenomenon. This phenomenon usually appears on the full version of a white background or light color background, because white or light color has worse hiding power.
 
2. Bubbles

Number	Cause	Solution
1	There is too much-left adhesive on the printing film, so there will have bubbles during the volatilization.	Controlling the solvent on the printing film in a certain range.
2	There has not enough surface tension so the glue would be uneven, and there will have bubbles in this area.	Controlling the surface tension in a certain range.
3	There is not enough glue, causing a big area of the bubble because the glue is not even.	Adding certain amount of glue.

Solvent-free PUA (Polyurethane Adhesive for Flexible Packaging Lamination)

Solvent-free adhesive is eco-friendly adhesive, it doesn’t emit the VOCs during the process. Also, it has the advantages of low cost, low energy waste, laminating speed is fast, and level of automation is high.
 

Component A	Viscosity (CPS/25℃)	Component B	Viscosity (CPS/25℃)
FA-818AF	1500-4000	FA-218BF	3000-5500
FA-876A	2000-4000	FA-276B	2500-4500
FA-876AH	2500-5000	FA-276BH	1500-4500
FA-825A	3000-5000	FA-225B	4000-7000

(Chart 1/Coating PUA solvent-free type product information)
  (Chart 2/Coating PUA solvent-free type product characteristic)

Flexible packaging is not a surprise when it appears in our daily life, so using eco-friendly adhesive is an important thing. Coating P. Materials provides adhesive for solvent-free flexible packaging that has the advantages of higher initial adhesion, soft and transparent, which can provide the customers a perfect and strong flexible packaging, at the same time protecting the environment of the earth together.  If you want to know more about the product information, please contact us.