In recent years, with the increasing environmental protection awareness, solvent-free laminating adhesives are more widely used in the flexible packaging industry. This article will introduce the advantages, problems and development trends of solventless adhesives.
Advantages Of Solventless Adhesives
1. Environmentally friendly
Solvent-free laminating composite adopts solventless adhesive, which will not volatilize VOCs nor produce any irritating odor. It solves the problem of residual solvents in the packaging, eliminating the erosion of the organic solvent on the printing ink, can also achieve cleaning production, conducive to environmental protection.
2. Energy saving
The solventless laminating machine does not need to be dried, which reduces energy consumption. Moreover, in the late-ripening process, the maturation temperature of the solvent-free composite is substantially the same as the dry composite, so the energy consumption is also relatively close.
Since there is no organic solvent, so no need to adopt explosive and warm measures during production, transportation, storage and use and no need to specifically build a warehouse for solvent storage, more importantly, there is no harm to the health of the operator.
4. High Efficient
The speed of solventless machine adopting solvent-free adhesive is generally 250 ~ 350 m / min, even up to 400 to 500 m / min, while the solvent-based adhesive composite is generally 150 ~ 180 m / min.
5. Low cost
a. The coating amount of solvent-free adhesive is usually from 1.3 to 1.8 g / m2, while dry composite is 2.5-4 g / m2, and therefore, the amount of adhesive consumption can be reduced by about 50% compared to dry composite.
b. Since the solventless composite process does not require a drying process, energy cost is effectively reduced. After calculating, the energy consumption cost of the solventless lamination machine is 1/15 of the cost of dry composite consumption.
c. From the production efficiency, the efficiency of the solvent-free lamination machine is 1.5-2 times higher than that of ordinary dry composite, effectively reduces production costs.
Problems Existed In Solventless Adhesives
1.A great effect on the smoothness of PE film
When the solvent composite ripening temperature is greater than 40 ° C, it has a great effect on solvent-free composite film which has the inner layer of a PE film, and it is easy to appear the phenomenon that friction coefficient increases obviously. This is mainly because the higher the ripening temperature, the more intensely moved the molecular motion of the PE film, which is easy to migrate to the adhesive layer and the reaction is consumed, resulting in the increasing friction coefficient of the composite film.
2.Aluminum plating layer transfer
Aluminum plating film, especially a polyester plating aluminum film, is prone to aluminum transfer during the solvent-free composite, thereby causing insufficient strength of the composite film peeling.
3.Dissolve with ink
During the solventless composite, the phenomenon of adhesive and ink phase dissolution may occur, especially the dye-type ink.
4. Low peel strength of aluminum foil composite
At present, for the solventless composite of the aluminum foil, since the peel strength is not enough, it is still necessary to satisfy the heavy-duty packaging and requirements for cooking resistance.
5. Frequent replacement of solventless adhesive types
With the development of the solventless composite process, many solvent-free adhesive suppliers have introduced general solvent-free adhesives, cooking solvent-free adhesives, aluminum foil special solventless adhesive, low friction coefficient no solvent adhesive, etc. Although the diversification of the product can meet the composite requirements of different materials, the flexible packaging company also has to clean the gluing equipment and solventless machine according to the different composite materials. Not only it wastes time, human resource, financial, but also has low production efficiency.
Development Trend of Solventless Adhesives
1. Functional solventless adhesive
Solventless adhesives should develop to functional products, such as DMF organic solvent mixture with content less than 20%, a product resistant to pesticide corrosion.
2.UV curable solventless adhesive
UV curable solvent-free adhesives have the advantages of fast curing speed, transparent peel strength, non-toxic, non-corrosive, energy-saving and environmentally-friendly, widely used for plastic/plastic, plastic/paper, plastic/metal film, or other materials rapidly solvent-free composite. At present, UV cured solventless adhesive has been developed, but it still needs to increase research and development efforts to launch more mature products to the market.
3.Solventless adhesive used in other industries
The solventless adhesives used for textile, automotive interiors and other industries, as well as paper including kraft paper, cardboard paper, ordinary paper, plastic including various transparent films, aluminum plating films, aluminum foil, should be developed.
Solventless adhesives bring great benefits to environmental protection, health, safety, cost, etc, but still, have some problems that need to be paid attention to. The future development trends of solvent-free adhesives are multi-functional, can be used with various materials in different industries.