The advent of solvent-free adhesive has changed the face of the packaging industry, literally. Manufacturers have come up with flexible packages like pouches and bags as per customer demand and liking. This new technique is gaining market share and increasingly finding favour due to lower weight, lesser storage space requirement, lower shipping cost and greater ease in customisation.
Polyurethane coatings are well known and have gained commercial acceptance as a protective and decorative coating for metal, wood, concrete, foam, and plastic in the aircraft, construction, product-finishing, textile and maintenance/architectural coatings markets.
What is solvent-less polyurethane packaging?
Solvent-less laminating adhesive systems are either two-component or single- component laminating adhesives. They are strong, non-yellowing, laminating adhesives with good clarity and resistance to temperature extremes and humidity.
Two-component systems combine an isocyanate component with a hydroxyl-functional component. Single-component systems are isocyanate-based and moisture-cure. As they are solvent-less, these systems are more environmentally friendly than conventional laminate adhesives containing volatile organic compounds (VOCs).
The isocyanate components can be blends of polyester and/or polyether components reacted with isocyanates.
Polyurethane laminating adhesives are used to combine multiple layers of films, foils and/or papers to meet performance requirements from general to medium and to high performance packaging.
In this dynamic environment adhesive manufacturers are coming up with current technologies that address all packaging requirements from general purpose to high performance specialty applications.
Globally 03 laminating technologies are available
Solvent-based adhesive;
Solvent-less adhesive
Water-based adhesive.
Laminating adhesives are supplied both as single- and two-component. Solvent-less laminating adhesive systems are used in the manufacture of flexible packaging. These products are specifically formulated for use on solvent-less lamination presses and can be applied to nylon, aluminium, polyester, polyolefin, paper, and other packaging substrates.
Solvent-less adhesive is metered on to substrate in liquid form then metered to a second substrate by heated nip. Application is through multiple rolls configuration.
Solvent-free adhesives also have some disadvantages like low initial tack, high viscosity, higher curing time, short pot life that requires meter-mix-dispense unit, requirement of skilled manpower, poor wet ability as solvent-based adhesive and migration of aromatic amine in thin films.
Besides all these disadvantages, growth of solvent-less adhesive in India is more than 30% in comparison to solvent-based adhesive, due to high productivity and environmental hazard.
The packaging industry is the fifth-largest industry in India. According to Union minister of state for commerce and industry E M Sudarsana Natchiappan, the annual growth rate of the industry is around 15 per cent per annum and it is expected to touch $32 billion annual turnover by 2015.
