The Basics of an Extrusion Coating Line

Paper Extrusion Laminating Machine

An extrusion coating line is a highly versatile industrial process for coating a molten film of thermoplastic on substrates like paperboard aluminum foil, film, and woven fabric. The resulting coated materials are used in liquid packaging, photographic, toothpaste tubes, flexible packaging, mill and industrial wrappings, and insulation backed films.

The upstream side of the line includes all auxiliary equipment that receives, mixes/blends and delivers material to the extrusion machine.

1. Extruder

As the name suggests, extruders are the heart of an extrusion coating line. They take in the raw material blends, melt them into a homogenous mix, and push it through external tooling under pressure to create an extruded product.

Extruders come in a huge variety of sizes and output capacities to accommodate different types of material. They range from small, low-volume lab extruders that can make thin-diameter medical swab sticks or plastic tubing to large production units capable of processing thousands of pounds of material per hour into plastic-composite lumber and decking or thick-walled pipe several feet in diameter.

Whatever the application, every extrusion coating line needs a master extrusion control to regulate its operation and maintain dimensional consistency across the finished substrate. Without this vital piece of equipment, an extrusion coating line wouldn’t be able to produce its end-use products.

2. Die

A die is an extrusion tool that molten plastic is forced through to create the required coating thickness. A wide range of die shapes and designs are available to produce different products, including bubble bags, retort pouches, medical packaging, insulation backed materials, and more.

extrusion lamination plant

These dies are built to withstand high shear and tensile stresses in the application, as well as the thermal shocks of the hot extruded polymer. They are also designed to handle multiple line speeds.

A variety of add-ons are available to help reduce production time and labor costs for the dies. These include urethane strippers, mechanical die-hole retainers in True-Set style, and backing plates. Corona treating of the die, nip, and film is also increasingly popular for its ability to improve bonding adhesion, enable lower extrudate temperatures, and promote higher line speeds.

3. Chilled Roll

The chilled roll is an essential component for a number of extrusion processes, including flat sheet and cast film, as well as coating operations. It works as a heat transfer device, so it needs to be designed for the specific process and have an appropriate functional profile.

Co-Extrusion Laminating Machine

A high-grade proprietary elastomer covers the surface of the chilled roll, which eliminates corrosion and scaling. It also reduces oxidation, which extends the lifespan of the chill roller and ensures that it performs at an optimum level.

The new ecovio 70 PS14H6 extrusion coating grade is food-contact approved, with good barrier properties against liquids and fats as well as excellent temperature stability. It can be used in a wide range of paper applications, from hot- and cold-food containers to wrappings and to-go cups.

4. Back Up Roll

The forged back up roll is a mill roll that supports the work roll and intermediate rolls for the purpose of avoiding deflection of the work roll and maintaining the yield and quality of the plate and strip rolling mill. It consists of a high grade steel with excellent wear resistance and journal toughness.

Coating lamination

SML offers both belt and gravure lamination, and a unique system called DoubleCoat that combines extrusion coating with hot melt lamination. With this patented process, materials that are considered incompatible can be joined to produce products with unequalled properties such as breathable, waterproof membranes.

A driven, ceramic treatment roll is available to treat conductive substrates, and a driven, rubberised press roll for web tension control. SML also offers an optional turret winder to enable complete automation and a quick roll change at full speed.

5. Winder / Unwinder

The final product is rewound to form a bonded laminate. The line is able to process thin aluminium foils as well as paper and paperboard.

The winders and unwinders are engineered for precision gauge control, splice speed, reduced waste and simplified changeovers. Each missed splice can cause production downtime and material waste, which is why we design our machines to minimize splices.

In addition, many of our clients use corona treating on their lines. Ozone treatment can improve bonding adhesion, reduce coating temperatures and allow higher line speeds. Our applications engineers will help you determine the best solution for your operation. They can also recommend surface treatments for your specific application.

Nonwoven Laminating Compounding Machine