Cold seal packaging involves sealing or wrapping a product using a cold seal adhesive formulation. It is used in many industries mainly where the other packaging adhesives do not meet their requirements.
They are commonly used for packaging food products like candy, chocolates and medical supplies like cotton and band-aids and other utility items like tissues and hand towels.
What differentiates the cold seal adhesive from other adhesives is its characteristic to bond with only itself. A packaging substance is usually coated with a cold adhesive on one side and is then brought into contact with another base coated with the same cold adhesive to form a cold seal bond.
This makes it different from other types of adhesives some of which need to use heat or pressure to form a bond. The heat adhesives require a heat source for to be able to form a bond but the cold adhesive can be used without a heat source. This expands its utility greatly to packaging assemblies where it is not possible to include a heat source.
Pressure-based Adhesive
A pressure-based adhesive does not need heat, but it relies on the application of pressure to form a bond. In the end, it also needs to be covered with a special paper to prevent the adhesive from sticking to anything else before it is used. The cold adhesive does not have this constraint.
Cold adhesive is a rubber or latex based formulation where natural rubber is mixed with other ingredients to create an adhesive with strong bonding properties. Ingredients like plasticizers and resins or copolymers like vinyl acetate and ethylene are mixed with the rubber latex base.
The end formulation is usually an aqueous material and is not toxic. It does not include any major inflammable compounds. Some form of an anti-oxidant is usually added to the mixture because rubber has a tendency to weaken when it reacts with oxygen.
The strength of the adhesive bond varies based on the ingredients used in the formulation. The manufacturer often designs a formulation with bonding properties specifically suited for a specific application.
As with small parts kitting, some products may require strong bond strength while others may require slightly less bonding for their packaging.
Pressure Has an Effect
As with most adhesives, pressure has an effect on a cold adhesive too. Applying higher pressure will usually form force a stronger bond. Giving more time for the adhesive to bond slightly increases the strength of the final bond.
Cold adhesives are mainly used for food applications because of their consistent seal strengths. This characteristic is vital for automated food packaging especially for candy, chocolate and baked products that have to pass through a form and fill packaging machine.
Food Industry
In addition to the food industry, cold adhesives are also used in medical packaging. Using special acrylic water based formulations so that it is non-allergic and yet retains its bonding properties, the adhesive can be used to package several types of medical supplies including cotton and bandages.
These formulations form superior bonds and last for a long time compared to other types of adhesives.
Since the cold seal adhesives can be exposed to food when they are used in food packaging, it is the user’s responsibility to make sure that it meets all FDA regulations.
