Modern sanitary products are complex, multi-layered assemblies. A typical diaper, for instance, may contain up to six distinct layers: the top sheet, acquisition distribution layer (ADL), absorbent core, core wrapping tissue, backsheet, and leg cuffs. Each layer is bonded to the next to ensure structural integrity. Holding these layers together—without compromising flexibility, breathability, or comfort—is the function of hot melt adhesive.
What Is Hot Melt Adhesive?
Hot melt adhesive (HMA) is a thermoplastic polymer formulation that is solid at room temperature but becomes liquid when heated (typically 130–180°C). Applied in a molten state, it cools and solidifies rapidly to form a strong bond between layers. The key advantage of HMA over solvent-based adhesives is that it contains no volatile organic compounds (VOCs), making it safer and more environmentally friendly.
Three Main Application Methods
The method by which hot melt adhesive is applied directly influences the bond strength, product stiffness, and overall comfort. The three most common application techniques are:
Spiral Spray (Spiral Spray): A swirl pattern where adhesive is applied as a fine, continuous spiral thread, creating multiple contact points. This method provides excellent bonding with minimal adhesive usage (typically 3–8 g/m²), resulting in the softest product with good breathability. However, it requires precise nozzle positioning and is less effective for high-strength laminations that require extensive bonding.
Ω (Omega) Pattern (Ω形刮涂): A continuous zigzag or wave-shaped bead that covers a wider area than spiral spray. This method offers moderate adhesive usage (5–12 g/m²), higher bond strength, but slightly reduced flexibility compared to spiral spray.
Slot Coating (狭缝涂布): A solid film or continuous layer of adhesive applied across the full width of the web. This method provides maximum bond strength (often 100% coverage), but at the cost of stiffness—the product becomes rigid and less breathable. It is typically used for non-critical laminations (e.g., core-to-backsheet bonding).
⭐Impact on Core Stability and Flexibility
The adhesive method directly affects core stability—the ability of the absorbent core to remain intact and distribute liquid uniformly. Higher bond strength (slot coating or omega pattern) prevents the core from shifting or delaminating, particularly in high-activity wear. However, higher adhesive usage generally reduces flexibility and softness, increasing the risk of skin irritation.
Baby Diaper
Baby Pull Up Pants
Adult Diaper
Sanitary Napkin
Wet Wipes
Tissues Paper
Disposable Cotton Soft Towel
Pet Diaper
