Hot melt adhesive: what are they and where are they used?
Hot melt adhesives are mainly composed of a mixture of thermoplastic polymers, resins and additives that are melted and applied to the surfaces to be bonded using special machinery, such as adhesive guns or roller applicators.
Once applied, the adhesive solidifies quickly, forming a strong bond between the adhering surfaces, which becomes permanent once cooled.
These adhesives offer several advantages over other types of adhesives, such as speed of adhesion, ease of application and the ability to adhere to different surfaces.
HOT MELT adhesives are used for:
- Packaging:
corrugated cardboard closure
closing primary packaging, such as boxes for biscuits, tea, etc.
labelling for surfaces that can reach high temperatures (automotive, industrial motors) - Production of self-adhesive labels
- Binding
- Wood, construction and furniture industry
- Textile
- Automotive sector
- Construction of equipment
Type of service required and plant characteristics:
A company with a chemical process plant in ATEX zone 1 produces thermoplastic adhesives and hot melt adhesives and needs to:
- Handle adhesives (solvent-free) with high and varying viscosities (5000 / 150.000 cSt)
- Install a single electric pump (made versatile by inverter control 10 - 75 Hz)
- Transfer the product to three different destinations (product verification, process line, packaging or storage tanks)
- Accurate flow and pressure control via PLC’s with signals from transmitters (flow rate / pressure / load cells)
- Installation area classification: ATEX - zone 1
- Suction system with very low NPSHd
Solution: Varisco V internal gear pump
Due to their heavy-duty design for viscous and highly viscous fluids, the V series internal gear pumps are particularly suitable for handling HOT MELT adhesives.
Varisco positive displacement internal gear pumps, model V 80-2A T8K+O2X+R2/R9,2/MX1004-I/P/V, is installed for this application:
- Construction material: AISI 316 stainless steel
- Certification according to ATEX directive - zone 1
- Vertical inlet orientation
- Installation under reactor with vacuum phases close to 0
Generally, depending on the chemical-physical characteristics of the fluids handled and the construction versatility of the pumps, different metallurgies can be used: cast iron, carbon steel and AISI 316 stainless steel (S...G - S...AW - S...K versions), available with either packing seal or single or double opposed mechanical seal).
The elastomeric materials are selected according to the type of adhesive, as are the materials of the seals, bushings, shafts and pins.
