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Unobstrusive but indispensable. Adhesives are probably as old as mankind itself is and have always been an irreplaceable part of our everyday lives. As early as the Stone Age, birch pitch was produced by dry distillation over a wood fire and used as an adhesive. Archaeologists were able to prove this during the excavation of a Stone Age weapons depot.
Nowadays, adhesives can be found in almost every everyday object. Like our everyday objects, the adhesives used in them are subject to constant evolution. This evolution has been massively accelerated in recent decades. Many new products and production processes have ensured that bonding as a joining technique has developed greatly. The adhesives market has increased rapidly over the last century. An enormous variety of different adhesive types has been developed.
Industrial Adhesives must meet high Requirements
The requirement profile of an industrial adhesive depends, for example, on the materials to be bonded. Plastics, wood and wood-based materials, metals and mineral materials are bonded together in countless applications. Depending on the purpose, an adhesive bond should have certain properties. Flexible, rigid, removable or permanently strong are typical requirements. Furthermore, long-lasting durability is important. Strong temperature fluctuations, chemicals, humidity, weathering or mechanical loads can stress an adhesive bond.
The requirements for the manufacturing process of a product and the associated economic efficiency also play a major role. Industrial adhesive systems are often processed in automated production processes. At the subsequent user, they are then brought to a processable state by means of special melting equipment and transported via suitable conveying units to the application units, such as a slot nozzle, spray nozzle or roller. The processing techniques in the adhesive processing industry are diverse. In most cases, the goal is always the same - high production speeds and a bond perfectly matched to the application.
Hotmelt and reactive hotmelt adhesives score for their high level of customizability
Every adhesive joint, including its production process, has its own specific requirements. Countless converting processes realize countless joining methods. In industry, hotmelt adhesives have proven to be particularly adaptable. Typical industrial sectors in which hotmelt adhesives are in use are listed below.
Non-reactive hotmelt adhesives
Non-reactive hotmelt adhesives are based on a thermoplastic base polymer. By adding further components, the adhesive can be precisely formulated to meet a desired requirement profile. These additives are usually synthetic resins, oils or waxes. Non-reactive hotmelt adhesives include, for example, EVA hotmelt adhesives, polyamide hotmelt adhesives or polyolefin hotmelt adhesives.
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EVA hotmelt adhesives - adhesives based on ethylene vinyl acetate
EVA hotmelt adhesives are widely used in industry. The reasons for this are a particularly good price-performance ratio and sufficiently good thermal stability.
EVA adhesives are used in the following industries, for example:
- Packaging industry
- Bookbinding industry
- Furniture industry
Polyamide hotmelt adhesives
Like EVA adhesives, polyamide hotmelt adhesives can realize significantly more specialized applications. Polyamide hotmelt adhesives are particularly resistant to chemicals and withstand a very wide temperature spectrum. With the right formulation, this can range from -40°C to +140°C. These properties are particularly important for the following industries:
- Automotive industry
- Filter industry
- Textile industriy
Reactive hotmelt adhesives
Technically advanced and incredibly adaptable are reactive hotmelt adhesive systems. These have several advantages over non-reactive adhesive systems. In addition to the physical curing of the hotmelt, a chemical reaction also takes place. The adhesive can no longer be melted after the chemical reaction, which has a positive effect on the quality of the bond in many respects. Reactive PUR hotmelts, for example, are highly resistant to temperature, water and mechanical stresses. The high flexibility in the adhesive formulation enables tailor-made adhesive systems to meet particularly high requirement profiles.
Reactive polyurethane hotmelt adhesives (PUR hotmelt adhesives)
Applications with reactive polyurethane adhesive systems are the highest level in adhesive technology. In the last decades, reactive polyurethane adhesive systems have developed strongly. With the right know-how, adhesive bonds of the highest quality can be realized. Such an adhesive bond has an enormous resistance to external influences. These are, for example, strongly fluctuating temperatures, continuous mechanical loads and resistance to chemicals.
Reactive PUR hotmelt adhesives enable extremely strong adhesive bonds, with perfectly coordinated production processes.
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Typical applications of reactive hotmelt adhesives are:
- Automotive industry
- Wood processing
- Furniture industry
- Shoes and textiles
- Filter production
- Electronic industry
Reactive Hotmelt Adhesives in Micro-Emission Quality
Emission-reduced products are currently setting the trend in the market for reactive hotmelt adhesives. In the context of the REACH regulation, the European Union has decided to make the handling of PUR adhesives even safer. The REACH regulation is intended to improve the protection of human health and the environment from the risks that can arise from chemicals. Furthermore, a general interest in low-pollutant and more environmentally friendly products is ensuring an increasing demand for emission-reduced PUR hotmelts.
In terms of bonding quality and processing properties, emission-reduced hotmelts offer identically good properties. In addition, they offer the following advantages:
- More environmentally friendly manufacturing process
- No labeling obligation with P and H phrases
- Safe and easy handling
- More cost-effective plant technology thanks to simplified extraction systems
- Identical bonding properties
Biobased Hotmelt Adhesives
PUR adhesive systems based on sustainable, plant-based raw materials are also on the rise. The important thing here is that the plant-based raw materials used are not suitable for food production. With bio-based hotmelt adhesives, excellent bonding performance can be expected, just as with conventional PUR hotmelts.
Adhesive bonding as the joining technology of the future
In recent decades, hotmelt adhesives have revolutionized joining technology. Adhesive bonding is still considered a very promising joining technique, with decisive advantages over many other joining methods. An ever-growing variety of different materials meets an enormously adaptable adhesive technology. The result is joints that are perfectly matched to the application and can be realized in a very economical production process.
As a general rule, an adhesive is only as good as its processing. The perfect adhesive bond is a close interaction between the formulation of the adhesive and its processing by the user. The KLEIBERIT engineers have decades of experience and have been able to provide significantly efficient solutions in the diverse areas of industrial bonding processes. KLEIBERIT's application-specific know-how is valued worldwide. Market-renowned manufacturers of adhesive processing machines, as well as adhesive processing companies from a wide range of industries, benefit from KLEIBERIT's extensive know-how.
An overview of the industrial applications in which KLEIBERIT adhesives are used can be found here.
Source of information
Möbelfertigung: Ausgabe 3, 2019 – Ligna Spezial. „Sichere Produkte sind in Jedermanns Interesse“