High-Speed Hot Melt Coating Technologies for Nonwoven Fabrics: Spray and Slot Die Systems
High-speed hot melt coating machines for nonwovens are essential for producing disposable hygiene products (diapers, sanitary napkins), medical drapes, surgical gowns, and filtration media at production speeds of 200-600 m/min. Unlike coating on films, nonwovens are porous, requiring careful adhesive application to prevent strike-through (adhesive penetrating to the opposite side) while maintaining fabric breathability and softness. The two dominant high-speed technologies are spiral spray (fiberized application) and slot die pattern coating. ITW Dynatec‘s Apex slot die technology delivers exceptional results for solid barrier applications, while UFD (Uniform Fiberized Deposit) spray allows customers to create products with controlled flow characteristics between composites. Nordson has over 50 years of experience in hot melt adhesive applications, with coating heads that can be combined with slot nozzle, screen printing, spray applicator, or gravure roller methods depending on specific requirements.
Spiral spray technology (also called fiberized spray or swirl coating) is the most common high-speed method for nonwoven lamination in hygiene applications. The system uses a heated nozzle with compressed air to atomize the hot melt adhesive into a fine spiral pattern. The “Spiral Spray” method applies hot melt in a fiberized form onto the substrate, achieving beautiful spiral application with minimal scattering regardless of low or high speeds. It achieves a soft finish with pleasant texture and breathability while reducing waste and loss of hot melt adhesives. High-speed intermittent adhesion is possible, with the spiral accommodating up to 72,000 rotations per minute and a width of approximately 15-20mm. Nordson’s Control Coat QE applicators fiberize hot melt adhesive for consistent, uniform pattern in high-speed nonwoven or web coating applications, using non-contact spray coating to provide excellent edge control and pattern definition. The configurable Nordson melt and metering units allow various types of hot melt adhesives, sealants, and other materials to be processed.
Hot Melt Coating Machine - Hot Melt Adhesive Coating Machine
Slot die technology offers an alternative for nonwovens requiring a solid barrier coating rather than an open pattern. For applications needing full coverage, ITW Dynatec‘s Apex slot die technology delivers exceptional results with non-contact, highly accurate slot applicators for wide web coating and lamination. Universal Converting Equipment’s CL1600 wide web machine features 1600mm maximum web width with running speeds from 10 m/min to 250 m/min and coat weights from 1 gsm to 200 gsm. The machine can apply hot melt adhesive using proximity coating slot dies or non-contact spray technology such as ITW Dynatec Dynafiber, with precise tension control for processing non-woven, paper, and plastic materials. Turret unwind and rewind systems are available for high-speed non-stop production, along with in-line adhesive coat weight scanning, in-line slitting, and differential rewind systems. Nordson’s CP 3000 generation screen printers provide an alternative for applying hot melt adhesive in varying sizes, patterns, and pictures, with screens custom-made for each application pattern that are economical and can be changed in minutes.
Key process parameters for high-speed nonwoven coating include adhesive temperature (typically 140-170°C for SBC-based PSAs), coat weight (2-20 gsm for lamination, 5-30 gsm for elastic attachment), and open time (0.5-2 seconds). Spiral spray achieves excellent coverage with low adhesive usage (2-5 gsm) while maintaining breathability because the open area of the pattern can be as high as 80-90% at low coat weights. The nozzle-to-web distance (20-50 mm) affects pattern width, while air pressure (0.5-1.5 bar) and adhesive flow are balanced to achieve the desired fiberization. For slot die pattern coating, a shim creates discrete dots (e.g., 1mm dots at 3mm spacing) for breathable bonding. The die is mounted close to the web, and a vacuum roll holds the nonwoven flat. Dot pattern reduces adhesive usage further (1-3 gsm) and gives an even softer feel compared to spiral spray. Many hygiene lines use a combination: construction lamination with spiral spray, elastic attachment with small slot die or spray, and core stabilization with spray patterns.
Defect prevention in high-speed nonwoven coating requires careful control of several factors. Strike-through (adhesive visible on the opposite side of the nonwoven) occurs when coat weight is too high, viscosity too low, or the nonwoven is too porous. Reduce coat weight, lower temperature to increase viscosity, or use a denser nonwoven substrate. Air entrainment (bubbles) at high speeds requires grooved backup rolls or vacuum assist. Non-contact spiral spray inherently reduces air entrainment because the adhesive fibers contact the web without trapping air. Adhesive stringing (threads between dots) can be reduced by increasing suck-back in the valve or raising temperature to lower viscosity. For slot die pattern coating, missing dots indicate screen clogging; regular cleaning with hot melt cleaner and compressed air is required. The backup roll should be chrome-plated steel with a release coating to prevent adhesive sticking. Web tension must be very low (2-4 N/cm width) because nonwovens have low tensile strength; use a dancer roll with light air pressure and a vacuum conveyor to hold the web flat.
Machine configuration for high-speed nonwoven coating includes a melt tank (often 100-200 kg capacity for continuous feeding), a gear pump with hardened gears for abrasive adhesives, a heated hose manifold, and multiple applicator heads for multi-layer lamination. Nordson offers melt rates from 1 to 1000 kg/hr with up to eight separately-controlled metering pumps per unit, and dual melt zones providing progressive melting to maintain the integrity of the hot melt adhesives. The line typically includes unwind stands with automatic splicing (turret unwinds), an accumulator festoon for continuous operation, the coating station with vision inspection, cooling section, and a turret rewind. For hygiene products, the machine must run 24/7 with uptime exceeding 95%. Preventive maintenance includes daily cleaning of spray nozzles or screens, weekly filter changes, and monthly calibration of temperature sensors. The Control Coat QE applicators are designed for high-speed intermittent operations, delivering outstanding cutoff performance even at the highest line speeds. By selecting the appropriate high-speed technology (spiral spray for breathable patterns, slot die for dot patterns or full barriers) and optimizing process parameters, manufacturers achieve efficient, high-quality nonwoven lamination that meets the demanding requirements of disposable hygiene and medical markets.
