Extrusion Coating and Laminating

In the first operation, the paper and the foil are extrusion laminated using an acid copolymer as the adhesive. Next, the sealant layer is applied as an extrusion coating. The operation can be accomplished in two passes, or in a single pass in a tandem extrusion line as shown in Fig. 8.2. In such a line, both extrusion heads are usually capable of coextrusion, as well. To understand the process of extrusion coating and laminating, it is necessary to start with the process in its simplest form, which, by the way, is how it is still practiced today by some converters. 

To reduce the need for such high temperatures, primers are used to improve adhesion. These primers are organic compounds that are coated onto the paper in-line with the extrusion coating to provide nonpolar groups to which the PE can adhere, as well as polar groups which can adhere to the paper. Polyethylene imine (PEI) is one such compound. These primers allow the melt temperature to be reduced to 288°C (550°F), so less oxidation occurs and there is less potential for off-odors. 

Primers can be used on foil also, but another approach often used with foil is to use a polymer that has polar groups on the chain, such as an acid copolymer or an ionomer, for the coating. Polyethylene acrylic acid is a typical acid copolymer, lonomers, as discussed in Section 4.1.4, are partially neutralized acid copolymers, of which Surlyn is the best known. Acid copolymers and ionomers can also be used as sealant layers. 

The tandem coating line seen in Lig. 8.2 can be used to reduce the cost of producing products that require both laminating and coating, such as a paper/poly-ethylene/foil/sealant type of structure. If this product is made in two passes through the machinery, the cost is higher because of the increased cost of handling the materials twice and the increased start-up and shut-down waste. 

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Nipolon. [Tosoh] Polyethylene resins used for blow molding, blown film, extrusion pipe, extrusion coating and laminating, inj. molding, filament... 

Cast Film Extrusion, Extrusion Coating and Lamination... 

Uses Barrier resin in sheets, films, pkg. materials, gas till pkg., pkg. for oily foods, edible oils, min. oils, agric. pesticides, org. soivs. suitable for film extrusion, sheet coextrusion, bbw molding coextrusion, tube profile coextrusion, extrusion coating, and laminating procedures Features Thermoplastic... 

Uses Adhesive polymer for extrusion coating and laminating, textile, lumber, plastic, rubber, metal, formed prods., paper, packing film, etc. Features Exc. adhesion with most substrates easy peel seals for plastic containers... 

Uses PE for blown film (pkg., heavy-duty bags, agric. film, diaper backings, stretch film, shrink film), extrusion coating and laminating (krafl papers, milk carton stocks, box liners), blow molding, inj. molding (housewares, artificial flowers)... 

A wide range of processes are used, ranging from thermal and adhesive bonding through to extrusion coating and lamination. 

We can see some examples of extrusion coating and lamination technology. 

Exhibit 7.2 provides more detail on the scale and sophistication of extrusion coating and laminating technologies. 

Exhibit 7.1 Extrusion coating and laminating schematic. Courtesy of CaPlast. 

The extrusion coating and laminating process can create an amazing range of products. 

Extrusion coating and laminating are ways to add value to the existing product line of spunbonded PP [165]. 

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