Nonwoven fabric hot melt adhesive coating machine
A nonwoven fabric hot melt adhesive coating machine is specifically designed to apply adhesive to lightweight, porous, and often heat-sensitive nonwoven substrates such as spunbond, meltblown, carded, or airlaid webs. Nonwovens are used extensively in hygiene (diapers, feminine hygiene, adult incontinence), medical (surgical gowns, drapes, masks), and wipes. The coating machine must handle very low basis weight substrates (typically 8-50 gsm) without causing burn-through, wrinkling, or excessive adhesive penetration. Common coating methods include slot die (for full or pattern coating), spiral spray (for open, breathable patterns), and dot pattern coating via gravure or screen. The machine must have precise tension control, often using dancer rollers with very low inertia, and a cooling section to solidify the adhesive before winding.
The working principle for nonwoven coating: The nonwoven unwinds from a roll, passes through a web cleaner (vacuum or tacky roller) to remove loose fibers, and then enters the coating station. For slot die coating, the adhesive is applied as a thin film or as patterns via a shim. For spiral spray, a spray gun with swirling air patterns applies a fine, open-fiberized adhesive pattern. After coating, the nonwoven may be immediately laminated to another nonwoven or a film (e.g., backsheet film for diapers). The laminate then passes over chill rolls set at 10-30°C to set the adhesive. The final product is rewound. Typical line speeds are 200-600 m/min for hygiene products. The coat weight is kept low, often 2-15 gsm, to maintain softness and breathability.
Hot Melt Coating Machine - Hot Melt Adhesive Coating Machine
Key applications: 1) Diaper construction – bonding the topsheet to the acquisition distribution layer (ADL) and the backsheet. 2) Elastic attachment – applying hot melt to elastic strands sandwiched between nonwoven layers. 3) Sanitary napkin – bonding the cover stock to the absorbent core. 4) Medical gown lamination – bonding nonwoven to a breathable film. 5) Wet wipes – interleaving adhesive pattern applied to allow pop-up dispensing. 6) Adult incontinence briefs – similar to diapers. The machines must produce consistent, low-add-on coating to avoid "strike-through" where adhesive penetrates to the product surface.
Special considerations: Nonwoven fabrics are often treated with hydrophilic or hydrophobic finishes, which affect adhesive wetting. The coating machine may need a corona treater upstream to increase surface energy. Tension must be low (e.g., 0.2-0.5 N/mm width) to prevent necking (width reduction). Edge guides are mandatory because nonwovens can shift laterally. For elastic attachment, the machine often includes a "elastic unwind" with controlled stretch ratio. The adhesive used is typically a styrenic block copolymer (SBC) based pressure-sensitive adhesive for construction or a polyolefin for elastic attachment. The viscosity is low (500-3000 cP) for spray or fine pattern coating.
Control and quality: The coating weight is measured online using a beta gauge or infrared sensor. For pattern coating, a vision system may verify dot geometry and spacing. A critical parameter is the "open time" – the time between adhesive application and lamination. For nonwovens, open time is typically 0.05-0.5 seconds; the machine must position the laminating nip very close to the coating head (within 100-300mm). The chill rolls must have a non-stick coating (Teflon or ceramic) to prevent adhesive pickup. Some lines also have an "offline" unwind for the second substrate.
Maintenance and troubleshooting: Nonwoven fibers can accumulate on rollers and dies, causing adhesive to wick and create strings. Regular cleaning with compressed air and soft brushes is needed. The die lips should be checked for nicks from fiber debris. If the nonwoven shows "burn holes" (melted spots), reduce the coating temperature or increase line speed. If the adhesive does not bond (peels easily), check the lamination nip pressure and temperature. Nonwoven hot melt coating machines are among the most advanced in the converting industry, requiring continuous innovation to meet the demands for thinner, softer, and more sustainable hygiene products.
