Isocyanate is a main building block of polyurethane and a key ingredient in reactive PUR hot melt adhesives. While some of the isocyanate is bound into polymers, the adhesive also contains a certain amount of monomeric isocyanate in the form of methylene diphenyl diisocyanate (MDI). These isocyanates are required for the crosslinking reaction and are largely responsible for the outstanding resistance to heat, moisture and other agents. However, melting and the chemical reaction in the adhesive can release gases which contain diisocyanate monomers and may under certain circumstances be acutely toxic. Depending on the concentration, diisocyanates have an irritating effect on skin, mucosa, eyes and the respiratory system. In addition, they can cause allergies. Precautions are therefore necessary to protect workers, for example by using an exhaust and ventilation system or providing appropriate personal protective equipment.
Conventional PUR hot melt adhesives generally contain about two to five percent of residual monomers (by weight) and must be labeled with the health hazard and exclamation mark pictograms according to the globally harmonized system of labeling (GHS).
However, under the currently applicable EU regulation and the subsequent amending regulation, adhesives are not subject to the hazard labeling requirement if the monomeric MDI concentration is less than 0.1 percent.
Sustainable adhesive solutions
Monomer-reduced—and therefore hazard-free—PUR hot melt adhesives have long been an integral part of Jowat’s Green Adhesives portfolio of highly sustainable bonding solutions for an extremely broad spectrum of applications in industry. The improvement in occupational safety is an important factor in decisions to change to these modern adhesives. In addition, monomer-reduced adhesives are often reported to be even better than their conventional counterparts in terms of performance.
Training will become mandatory
Adhesives with hazard-free labeling also facilitate considerable savings: As of August 24, 2023, all employees, including those involved in transport, who handle adhesives containing diisocyanate will be required to have completed a special training. Making sure and documenting that everyone has been trained costs time and money.
“Jowat has been providing monomer-reduced alternatives for over 20 years. Our customers can process these alternatives and avoid the additional training effort,” explains Maik Johanntoberens, product manager at Jowat SE. “We see it as our responsibility to accompany our customers with competent advice throughout the changeover process to ensure a successful outcome.
Hazard-free production is possible
The adhesive manufacturer from Detmold has developed the world’s first PUR hot melt adhesive with hazard-free labeling for window profile wrapping in accordance with RAL-GZ 716: Jowatherm-Reaktant® MR 604.90. Hazard-free production processes without downsides are now possible across the window and building element industry.
“Reduced monomer content does not equal reduced performance. The difference is made by the raw materials, the formulation and the entire manufacturing process,” Johanntoberens proudly explains and adds: “Our hazard-free adhesive impresses with outstanding resistance to hydrolysis and a high initial strength, particularly when laminating profiles with complex geometries. Coupled with our certified NEP-free and VOC-reduced primer Jowat® 406.84, it facilitates the bonding of widely established decor foils based on PVC and PMMA. Requirements of RAL-GZ 716 are not only met but exceeded. High peel strength data or foil tearing in roll peel tests according to DIN EN 1372 can be expected twelve hours after lamination already.”
Maximum flexibility
In most cases, the change from classic PUR hot melt adhesives to a PUR MR hot melt adhesive is said to easy and uncomplicated. Jowatherm-Reaktant® MR 604.90 can be processed on established wrapping units with common parameters. The enterprise describes it as a true “all-rounder” that provides maximum flexibility for the processor in terms of feed speeds, from six to forty meters per minute.
Johanntoberens sees monomer-reduced adhesives as a long-lasting success story: “Our high-performance products with hazard-free labeling provide future-oriented technical solutions for the bonding processes of our customers, under consideration of increasingly stringent economic and ecological requirements and with a vision of promoting healthy work environments. From profile wrapping to the lamination of building elements in general—our product portfolio provides a matching solution.”
Jowatherm-Reaktant® MR hot melt adhesives with hazard-free labeling are part of the Jowat Green Adhesives. The portfolio provides solutions for Jowat’s customers who are aiming for more sustainable manufacturing processes. Apart from products focused on occupational safety and health, the adhesive expert from Detmold also provides solutions that conserve resources. The portfolio is rounded off with adhesives based on renewable raw materials.
The article is published in the magazine ''bauelemente bau 04/2023" in German language. You can download the original article down below. Source: www.bauelemente-bau.eu