What is solvent-based laminating adhesive?

Solvent-based laminating adhesive is the most common type of glue in some sectors due to its adhesion properties and fast drying.

Using a solvent-based adhesive gives manufacturers peace of mind that the material remains firmly attached to the film throughout the manufacturing process.

These high-performance adhesives make up approximately 15% of the most demanding flexible packaging units. Some common products in this packaging category include laundry detergents with aggressive ingredients, medical applications, pet foods, and baby meals that are filled under sterile conditions.

What is Solvent-based laminating adhesive?

Solvent-based laminating adhesive is a type of adhesive that contains organic solvents as carriers of adhesive resins in the adhesive system. These solvents are dried after application to facilitate a process called dry bond lamination, which causes the active resin system on the substrate to bond to a secondary substrate to form a layer between the film and foil materials used to make the flexible packaging.

These adhesives provide good green bond strength. They also provide packaging and laminate materials with good appearance and high thermal and chemical resistance.

Important points regarding the application of Solvent-based laminating adhesive

These adhesives, which are used in flexible packaging, are usually two-component polyurethane adhesives. These are designed for use in the dry lamination process. The dry lamination process means a solvent that acts as an adhesive carrier and is applied to the primary layer and film.

The solid percentage of mixed adhesive implementation depends on the weight of the dry coating of the desired adhesive and the cell depth of the existing rotogravure cylinder. Solids content is critical to obtain the desired dry adhesive coating weight. It is always recommended to mix and dilute the adhesive with a known solid content and then maintain the viscosity of that solid content.

Ethyl acetate or toluene is the preferred solvent for dilution, while other compatible solvents such as acetone, methyl acetate (MEK), and isopropyl acetate (IPA) are available, but these solvents have low odor threshold levels, so extreme care must be taken. to ensure that they are completely dry. Solvent purity plays a vital role in the preparation and application of adhesive. Solvents should not be contaminated with water. The water content in the solvent should be less than 0.1%. The water content of the solvent may interact with the bonding reaction of the adhesive, leading to delayed curing of the adhesive along with other problems such as foaming after mixing and reduced pot life of the adhesive mixture.

Two-component solvent-based polyurethane laminating adhesives must be mixed according to the ratio mentioned in the technical data sheet of the adhesive. Apart from the purity of the solvent, the pot life of the solvent-based laminating adhesive depends on the solid percentage and the ambient temperature. At higher ambient temperatures, the solvent evaporates, resulting in increased viscosity, which ultimately leads to application problems. This can be avoided by regularly checking the viscosity of the mixed adhesive and by adding solvent at regular intervals. If this is not done and the viscosity is too high, the adhesive may react with moisture, resulting in the formation of small gel particles.

It is always recommended to use the mixed and diluted adhesive within 8 hours of preparation.

However, if there is any adhesive left at the end of the shift, you should store it in a sealed container after adding plenty of solvents. The next day, if the remaining adhesive is clear and without gel, it can be used again by adding a small amount of this adhesive to the freshly prepared mixed adhesive.

In solvent-based lamination, dry adhesive is usually applied at 1.5 to 3.5 grams per square meter, depending on: the Ink GSM, the structure of the film, the laminate, and the final application of the laminate. Higher coating weights are required for end applications such as hot filling product and packaging of liquor and aggressive and corrosive materials where high chemical resistance is essential. The thermal and chemical resistance of the adhesive deteriorates if the solvent is retained in the laminate. The temperature of the nip cylinder helps in the smooth transfer of the adhesive onto the secondary layer, thereby improving the bond strength. The temperature of the nip roller varies depending on the thermal sensitivity of the laminated substrates.

Solvent-based laminates cure within 24 hours when stored at ambient temperature and can be cut for further processing. Thermal and chemical resistance is created in 3 to 7 days of laminate. The curing speed can be accelerated by keeping the laminated rolls in a hot room.

What are the advantages and disadvantages of solvent-based laminating adhesive?

Advantages of using solvent-based lamination adhesive

The solvent in the adhesive is able to etch the substrate. This means that you don’t always have to prepare the surface to achieve a strong bond.

The solvent can break down the adhesive into a paste. This makes it easier to spread on the substrate surfaces when applying the adhesive.

Solvent-based lamination adhesive has better temperature stability. This means they can withstand colder temperatures than solventless lamination adhesives. Solvent-based laminate glue also resists better in weather conditions.

Solvent based laminate adhesive can achieve faster curing time. Solvents in adhesive evaporate moisture even at low temperatures. This means that solvent-based laminate adhesive is also less dependent on having the right conditions for curing.

Disadvantages of solvent-based lamination adhesive

An example of a harmful solvent often used in adhesives is methyl ethyl ketone (MEK). Any adhesive containing more than 5% MEK qualifies as a solvent-based adhesive.

Some of these adhesives can be dangerous to health. This is the clear reason that most flexible packaging manufacturers use less solvent-based laminating adhesive. Some solvent-based laminating adhesives are obviously more harmful than others, but you should be aware of the risks before using them.

Most solvent-based laminating adhesives on the market are flammable. The vapors that solvent laminate adhesives tend to emit can be flammable. When the concentration of these vapors is high, the risk of their ignition increases significantly.

They can damage the substrate they are connecting to. This is a problem because it can damage the aesthetics of the substrate it is bonding to.

Namitac solvent-based laminating adhesive

These adhesives are known for their stability, flexibility and transparency in certain laminates. Due to the lack of emulsifiers and surfactants, the resistance of solvent-based laminating adhesives against moisture is superior to existing water-based systems. One of the most popular solvent-based laminating adhesives is polyester laminating adhesive. Initially, polyester-based resins were introduced for polyester film lamination, which contain relatively little solids and have excellent adhesion to polyester film and good adhesion to many They create other polymer films and metal foils.

The reaction of hydroxyl polyester with polyisocyanate creates an adhesive network with very good thermal and chemical resistance. In general, polyester adhesives have high green strength, act relatively quickly and are suitable for fast production processes.

When faced with a specific set of packaging requirements, choosing the most suitable raw materials for laminating adhesives is critical to achieving the most effective solution. Taknam Keyhan Polymer Company’s Namitac solvent based laminating adhesives have high adhesion strength, suitable viscosity with special features and can be used for a number of applications and flexible packaging substrates. These adhesives, containing a solvent as a carrier, subsequently dry after application to the film surface, leaving the active resin system on the substrate to bond to a secondary substrate to form a laminate.

These laminates can contain multiple layers and can be used in a variety of food packaging applications, including high-demand and recyclable packages that comply with FDA regulations.

Namitac solvent-based laminating adhesives are designed for non-food (detergent packaging, etc.) and indirect food applications. Flexible packaging laminates made with Namitac solvent-based laminate adhesives can be used in a variety of food packaging applications including snack foods, meats, cheeses, frozen foods, chemically challenging foods, and oily or fatty foods. Namitac solvent-based laminating adhesives also meet multiple FDA food packaging regulations, enabling demanding applications such as pouch, cookable, hot filling, and returnable packaging. Taknam Keyhan Polymer’s solvent-based laminating adhesives are one of the most widely used adhesives in the industry. For more information on Namitac solvent based laminating adhesive, visit the products section of our website.

These products have a short curing time, excellent initial adhesion and a short delay between the time of lamination and cutting. Taknam Keyhan Polymer’s sales and R&D departments can provide guidance and support to ensure that your food packaging staff is trained and supported to execute your specific programs.