Pattern coating process with hot melt adhesive
The pattern coating process for hot melt adhesive is a specialized technique that applies adhesive in a discontinuous, precise design rather than a full, solid layer. This capability is a key strategic advantage for manufacturers, allowing them to create high-performance products that require breathability, flexibility, or targeted bonding. Common patterns include precise adhesive dots, a grid-like matrix, or parallel stripes. Pattern coating is achieved through several methods, most notably using a rotary screen, a gravure roll, or a slot die with a specially patterned shim.
Rotary screen printing is a leading pattern coating method, highly regarded for its precision and versatility. In this system, a PUR adhesive is transferred onto the substrate through a cylindrical, rotating screen, much like a traditional textile printing process. The adhesive is fed from a drum melter through a heated hose into a traversing dispenser inside the rotary screen. A doctor blade then presses the adhesive through the tiny holes in the screen, directly transferring the defined pattern onto the material below. This system offers exceptional flexibility; the pattern can be changed by simply swapping the screen, and different screen thicknesses allow for variations in coating weight and coverage without any mechanical changes to the machine.
Hot Melt Coating Machine - Hot Melt Adhesive Coating Machine
Pattern coating provides three direct functional benefits. First, it reduces waste, as adhesive is applied only where it is needed, which also reduces product stiffness. Second, it creates a liquid pathway by leaving uncoated spaces between adhesive dots, which is essential for high performance in sportswear and rainwear. Third, it allows manufacturers to achieve stronger bonding with less adhesive by depositing the material directly on the fabric's surface and preventing it from penetrating the fibers.
Another common method for pattern application is gravure coating, which uses an engraved metal roll with microscopic cells. The roll picks up adhesive from a heated reservoir, the excess is doctored off, and the pattern is printed onto the substrate as it passes between the engraved roll and a rubber backup roller. For coarse or intermittent patterns, a slot die equipped with a patterned shim is a simple and effective solution; the shim physically blocks the adhesive flow in specific areas, resulting in a coated pattern of stripes or discrete lanes. In contrast, some manufacturers use a closed pattern coating system to apply precise vertical beads of adhesive, which can be distributed at various angles. This method is particularly popular for applying two elasticated strands to a web, providing a strong yet flexible attachment.
The choice of pattern coating method depends on the required resolution, production speed, and adhesive type. Screen printing is generally preferred for high-resolution, fine patterns, especially in textile and garment applications where breathability and a soft feel are critical. Gravure coating is an excellent, high-speed option for replicable, lower-resolution patterns like a uniform dot matrix. Pattern coating is now the standard technology for high-value applications such as diaper elastic attachment, breathable medical tapes, and high-end filter assembly, where the precise placement of adhesive directly translates to superior product performance and customer satisfaction.
Looking forward, pattern coating technologies are evolving to become even more efficient and sustainable. The development of new screen and gravure designs allows for ever-finer adhesive application, using less material to create a stronger bond. When considering a pattern coating system, it is important to evaluate the cost of consumables: for example, rotary screens can cost as little as 10% of the price of a comparable gravure roller, offering a significant long-term economic advantage.
