Hot melt spray coating system
A hot melt spray coating system uses compressed air or other gas to atomize molten hot melt adhesive into fine droplets, which are then directed onto a substrate. This method is ideal for coating large areas, porous materials, or irregular surfaces where a continuous film is not required. The system consists of a melt unit, a heated hose, a spray gun (or multiple guns in a module), and a control unit for air pressure and temperature. Spray patterns can be adjusted from narrow beads to wide fans, and the coating can be applied in swirl or random fiberized patterns.
In operation, the hot melt adhesive is melted and pumped to the spray nozzle. Simultaneously, heated compressed air (to prevent adhesive cooling inside the gun) is mixed with the melt, causing it to break into filaments or droplets as it exits the nozzle. The substrate passes under the spray, and the adhesive droplets solidify upon contact. The open pattern allows the substrate to remain breathable (important for nonwoven fabrics) while providing sufficient bond strength. Spray coating can be intermittent or continuous, controlled by solenoid valves.
Hot Melt Coating Machine - Hot Melt Adhesive Coating Machine
Primary applications of hot melt spray coating systems include: 1) Hygiene products—spraying construction adhesive to hold absorbent core layers in diapers, or spraying elastic waistband adhesive. 2) Automotive—applying noise dampening adhesive to carpets or foam liners. 3) Furniture—bonding foam to fabric for cushions. 4) Filtration—spraying adhesive onto filter media to assemble pleated filters. 5) Mattresses—bonding layers of foam, batting, or ticking. 6) Garments—fusing interlinings without affecting hand feel.
Advantages of spray coating: it uses less adhesive than full-coverage methods (saving up to 50% material), produces a flexible bond that does not stiffen the product, works well on heat-sensitive substrates because the droplets cool quickly, and allows selective coating of only desired areas. The open pattern also prevents "strike-through" on porous fabrics. Another benefit is that the spray system can be retrofitted to existing laminators or converting lines easily.
Considerations: spray coating requires a clean, oil-free compressed air supply and careful temperature control to avoid adhesive stringing or poor atomization. The nozzle orifices are small and can clog if the adhesive contains gels or char. Maintenance involves regular cleaning of nozzles, replacing air caps, and checking air line filters. Spray pattern width is typically adjustable from 10 mm to 300 mm per gun, and multiple guns can be ganged for wider webs. When selecting a hot melt spray coating system, evaluate the droplet size range (from 100 µm to 500 µm) and the open time needed for your substrates. For high-speed lines (over 300 m/min), swirl spray modules are preferred for their stability. This system is especially valued in nonwoven converting for its combination of low add-on weight and high bonding performance.
