Over the past decade, more and more companies have abandoned rigid packaging for consumer goods and instead, adopted flexible packaging understanding that the attributes will benefit both the consumers and themselves as the brand owners. Flexible packaging is made of multiple layers of different kinds of films. This step is based on the desired protective properties to protect the product.
And, the final composition is always according to the requirement of brand owners and the nature of their products. Moreover, this procedure of combining films is known as lamination. But at the same time, there are different technologies used to manufacture the finished film used to make the packaging and brand owners should be aware of what they are and how they may impact a product.
This article focuses on two common processes used to bond the different film substrates to create the finished packaging material, one using a solvent-based adhesive and one using solventless adhesive.
Before moving on to solventless or solvent-based adhesives, here is some key information on lamination processes that will help you understand how these layers are laminated together by using the following lamination processes.
In dry lamination, the bonding agent is applied on the substrates that have been dissolved into a liquid. The dissolved substrate is dried in an oven to evaporate the remaining bonding material. Lastly, the adhesive is applied to this substrate, which is laminated to another substrate with the help of high pressure and heated rollers. This practice strengthens the bond of the laminate as well.
In this process, the combining agents are kept in liquid form when substrates are needed to be combined. Wet lamination is best for the production of aluminum foil or paper laminate where the material is also flexible.
The solvent is not used when it comes to producing adhesive substance. Also, opting for solventless adhesive needs two or more substrates, which react during this lamination process and there is no need for any drying component. This process results in the laminated web which is rewound into the complete roll.
In this process, the bonding agent is hot and in a melted form, which is applied to one substrate.
What are Solventless Adhesives?
Solventless adhesive is used in a wide array of packaging applications as it is a high-quality laminating adhesive. That is why solventless adhesives have become a crucial part of the laminating industry in a short time. Previously, these adhesives were used in certain applications only, such as snack foods, bottle labels, and candy bar wrappers.
In current times, solventless adhesives are used virtually in many applications. Take note that in traditional practices, solventless adhesives did not go well in things that contain foil. However, after significant improvement in this context, they have now made their way into applications that have foil in them including high-barrier films and high-slip films.
Benefits of Solventless Adhesives
Solventless adhesives come with a variety of benefits. For instance, these are great to lower coat weight. Moreover, using solventless adhesives means there is no solvent and no risks of emissions. Plus, there is no need to use ovens as well.
Its benefits also include that it runs at high speed using less energy. If you enter the market for the first time, using solventless adhesives can reduce your capital investment costs as compared to solvent-based laminators. On the other hand, the footprint is also minor in comparison to a solvent-based laminator.
Flexible Packaging Generations
There is no doubt that flexible packaging has become the need of the time. Therefore, adhesives manufacturers have tried to address this issue by generating several generations of flexible packaging of products. Not to mention, each variety is better than its predecessors when it comes to performance, regulatory compliance, and processing.
The first generation is based on one component solventless laminating adhesives that have sturdy green bond strengths and high viscosity. However, it requires high temperatures for application, which range typically between 80ºC and 90ºC.
The second generation, on the other hand, has two reactive components that have lower viscosity than the first generation. When it comes to laminate, it has medium to high residual isocyanate monomer and minimum initial bond power. The third generation laminating adhesives are produced to address the shortcoming in previous generations. With moderate-viscosity polyurethane polymers, it needs application temperature ranging from 50ºC to 70ºC only.
However, the fourth generation offers improvement by lowering viscosity and isocyanate-monomer without increasing cure times. And, LPS industries widely opts for fourth-generation adhesives that are VOC-free when it comes to flexible packaging varieties.
Application of Solventless Adhesive Flexible Packaging
Flexible packaging film is mainly applicable to consumable goods that need an extended shelf-life. This means that solventless adhesive flexible packaging film is suitable for products like the following.
- Ready-to-eat foods
- Frozen goods
- Fresh Produce
- Boil-in-bag pouches
They’re also ideal for packaging non-food items, like medical supplies, stationery, and cosmetics as well.
Because of constant development and research, today’s adhesives offer many benefits to product manufacturers along with increasing customer satisfaction and keeping the environment safe from harmful VOCs.