Technical Bulletins

Selecting Amide Slip Concentrates for Polyethylene Film Applications - Formulating Guidelines

Formulating Guidelines:

Optimization is the key to formulating with erucamide and oleamide slips. As previously stated, too much slip of any kind in roll stock can result in a telescoping effect which renders the rolls unusable. Excessive slip levels can also have an adverse effect on corona treatment levels and may interfere with adhesion of aqueous-based printing inks or cause problems in subsequent laminating operations.

Most conventional LDPE and LLDPE film resins exhibit COF values in the range of 0.60 to 0.75 while values of 0.80 to 0.95 are often typical of highly amorphous polyolefin elastomers such as EVA, EMA, EnBA, VLDPE and ULDPE. For most packaging film applications, reducing the COF levels to 0.2 or less results in significant improvements in film quality, increases film throughput rates and enhances handling properties such as rapid rewinding. Slip levels of 500 to 3000 ppm are typically required to decrease COF values to this level.

Since changes in primary resin characteristics such as melt index, density, comonomer content and type can greatly affect the performance of oleamide and erucamide slips, optimization studies are highly recommended. When formulating for standard 1-3 mil polyethylene film applications, 750 to 1000 ppm of slip is a good starting point for testing. Typical COF values for LDPE film as a function of amide concentration are shown in Figure 3.

In general, slip addition levels should be increased:

when using an amorphous polymer with a low degree of crystallinity (i.e. low density values)

to offset the higher surface-to-volume ratio when down-gauging films

when processing at higher temperatures in order to compensate for loss by volatilization (particularly      important with oleamide slip)

to offset physical absorption of the slip additive and increases in surface roughness when incorporating      high levels of solids in the film (i.e. fillers, pigments, antiblocks, etc.)

The use of oleamide and erucamide slip masterbatches are highly recommended in order to achieve uniform slip addition at low incorporation levels. Colortech offers two slip concentrates based on oleamide and erucamide chemistries for use in the manufacture of polyethylene blown and cast films. Colortech 10002-12 Oleamide Slip and 10003-12 Erucamide Slip consist of a 5.0% loadings of amide slip agent in a 5 melt index linear low density carrier resin. Figure 4 illustrates the addition rates for Colortech 10002-12 Oleamide Slip and 10003- 12 Erucamide Slip needed to achieve specific slip additive levels in finished film.

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