Masterbatch/Color Concentrate - Extrusion Coating

Within the polymer processing industry, the term extrusion used alone frequently refers to the profile extrusion process where the molten polymer is forced through a shape die (i.e. pipe, molding, etc) into a lineal cross section which is then cooled to a solid piece and cut to length.

Extrusion coating refers to the process wherein a flat die, similar to a cast film die, extrudes a curtain of melt which is laid down on a substrate (i.e. paperboard) where it adheres, cools, and forms a thin polymeric coating.

Extrusion coating is probably the most demanding process for TiO₂ due to the very high processing temperatures (>600 F) required to initiate degradation of the lightly or unstabilized polymer (typically LDPE) to allow it to bond intimately with the substrate before cooling.

A subset of extrusion coating is the wire coating process which operates at far less demanding conditions.

Profile Extrusion: This process relies on melt strength and low elasticity in the polymers processed which are primarily PVC, ABS, and HDPE.

The TiO₂ requirements, with the exception of durable PVC, are minimal since the profile cross section is usually thick enough to impart opacity on its own. Therefore, profile extrusion is far from a dispersion critical application.

The pipe market, while a large consumer of resin, uses very low TiO₂ loadings and is often content with low-grade products or substitutes. Some profile applications can demand brightness and whiteness but an NSF listed, general purpose TiO₂ is more than adequate for general profile applications.

Extrusion Coating: This process, as outlined above, is extremely demanding of TiO2 and the incorrect choice of TiO₂ can result in serious quality problems and equipment downtime. While general purpose TiO₂ has been used successfully in extrusion coatings, a high performance TiO₂ will perform more consistently in this hostile processing environment as it is designed for low volatility.