In extrusion coating applications, resin is melted and formed into thin hot film, which is coated onto a moving, flat substrate such as paper, paperboard, metal foil or plastic film. The coated substrate then passes between a set of counter rotating rolls that press the coating onto the substrate to ensure complete contact and adhesion.
Equistar offers a wide range of resins for extrusion coating, including Petrothene® low density polyethylene (LDPE) and linear low density polyethylene (LLDPE); Alathon® high density polyethylene (HDPE) and Ultrathene® ethylene vinyl acetate (EVA) copolymers.
Benefits and Applications
Some important applications for polyethylene-coated substrates are:
- Food board used to make cartons for packaging milk, liquid, powdered and solid foods, chemicals, fertilizers and resins
- Food pouches, such as those used for sugar and powdered food
- Multi-wall bags, such as those used for shipping food products, chemicals, fertilizers and plastic resins
- Lumber and steel overwrap
- Moisture barriers
- Cheese wrap
- Document sealing
- Medical packaging
- Liners for cartons, corrugated shipping containers and fiber drums
- Vacuum-forming materials for blister packaging and other special types of packaging
- Book or booklet covers
- Military packaging
Properties
The basic reasons for applying a polyolefin extrusion coating to a flexible substrate are to:
- Provide moisture barrier to either keep moisture out of packaged goods or to keep moisture in
- Increase tear, scuff and puncture resistance
- Gain a heat sealable surface
- Provide grease, oil and chemical resistance
- Provide adhesion between multiple substrates
- Improve package appearance